OCW Results (Confirm nodes)

[CK1.0]

What's sad is, while I obviously don't buy much, if any, of the node/OCW stuff... I have to admit that I don't think that totally gets every one of us off the hook from shooting a ladder now and again depending on what you're looking for.

Because, (related to what @Cascade Hemi is saying) I DO believe there are better charges than others for a given cartridge, better (not optimum lol) fuel to volume ratios/case fill amounts, that work better than others that you can see downrange if you're willing to shoot enough rounds to hopefully know you're actually seeing something real and not just noise.

But, again, I'm not talking about any specific/magic charge weight that's magically better than others, just a ratio/zone where vertical stringing seems to be lessened, and where the rounds may appear to clump together, which is a clue as to a safer/better place to park yourself as temperatures change throughout the course of a day/match.

Ironically, in my experience this seems easier to discover when shot at distance, say 400-600 yards, and far harder to tell if you're bullshitting yourself or looking at noise when shot at 100... but, the distance also adds noise due to all the extra shooter and weather-induced variables that could fuck things up... so at best it's far closer to a hunch than gospel.

For the "good enough for PRS" accuracy I'm looking for (i.e. minute-of-tennis ball at 600, softball at 750, cantaloupe at 1000), jumping at least 0.040" off the lands or more (these days usually ~.100" off in 6mm with 112gr Match Burner VLD's), I don't even worry about the ladder stuff anymore unless my waterline looks all wonky.

 

[Cfshooter]

It’s pretty much the same as many others at this level, I just skip the “charge node” stuff.

Highly simplified version:
1) research the bullet/cartridge combination and what other people have experienced that has worked well for them. Once I find a jump that seems to match the best crowd sourced on census, I start with that.

2) work up powder in .25 gn increments (one shot) from minimum to max until I find the approximate charge I need to safely achieve my target velocity (as I have a speed I’m looking for depending on the intended use of the load). This is with the searing depth I started with through research and my specific chamber (freebore, etc.)

3) load 5 rounds per a 0.002” increment in seating depth from baseline towards jam for approximately 12 thousandths of overall change between shortest and longest test cartridges.

4) look for approximately 6 thousandths wide spans within that sample that shoot noticeably better compared with the 6 thousandths gaps in between them (this can vary either way a few thousandths).

5) pick the longest bullet seating depth in that 6 thou window and load 25-50 rounds and shoot them in succession in 5 shot groups. Sometimes I’ll shoot 10 round or more for the group, it doesn’t matter because the last step I overlay all these groups and look at the mean dispersion diameter. If it works for what I’m trying to achieve with that load, then I’m done.

Of note: if your SD/ES is not acceptable for your intended use, look at your brass resizing process as that has the most impact.

This is just my process and should not be taken as gospel. I am however a firm believer through experience and shared experience with others that’s “ocw” is a waste of time.

What do you use to overlay groups, is it some type of program? I t
Do it with more of a photo program and it isn’t the best, hard to see all shots clearly after about 3 targets.

 

[Cfshooter]

What's sad is, while I obviously don't buy much, if any, of the node/OCW stuff... I have to admit that I don't think that totally gets every one of us off the hook from shooting a ladder now and again depending on what you're looking for.

Because, (related to what @Cascade Hemi is saying) I DO believe there are better charges than others for a given cartridge, better (not optimum lol) fuel to volume ratios/case fill amounts, that work better than others that you can see downrange if you're willing to shoot enough rounds to hopefully know you're actually seeing something real and not just noise.

But, again, I'm not talking about any specific/magic charge weight that's magically better than others, just a ratio/zone where vertical stringing seems to be lessened, and where the rounds may appear to clump together, which is a clue as to a safer/better place to park yourself as temperatures change throughout the course of a day/match.

Ironically, in my experience this seems easier to discover when shot at distance, say 400-600 yards, and far harder to tell if you're bullshitting yourself or looking at noise when shot at 100... but, the distance also adds noise due to all the extra shooter and weather-induced variables that could fuck things up... so at best it's far closer to a hunch than gospel.

For the "good enough for PRS" accuracy I'm looking for (i.e. minute-of-tennis ball at 600, softball at 750, cantaloupe at 1000), jumping at least 0.040" off the lands or more (these days usually ~.100" off in 6mm with 112gr Match Burner VLD's), I don't even worry about the ladder stuff anymore unless my waterline looks all wonky.

Minute of tennis ball at 600 yards? That’s just good enough? That would win me some f class matches.

 

[thepatchcable]

This blew up, I'll have to read through it.

 

[Cascade Hemi]

This blew up, I'll have to read through it.

Excuse me sir, I'd like to tell you about my lord and savior Amp Annealer.

 

[CK1.0]

Minute of tennis ball at 600 yards? That’s just good enough? That would win me some f class matches.

IDK, sometimes it is, sometimes it isn't... usually, it's the monkey pulling the trigger who fucks things up, not the gun/load IME lol.

IMHO I think 1/2 MOA is fair in so far as what most of us can expect on the regular if we're using good/proven components (both rifle and reloading-wise) and put some work into stepping up our reloading game. FWIW, I come from the point of view that I'd rather 1/2 MOA always, over 1/4 MOA if I keep it in tune and nearly jam it... I want that extra ~1000rds or so of barrel life out of a barrel and I'm more after consistency/repeatability that I don't have to really think about again once load development is done. If I shot F-Class, I'd think about it and approach it differently since I'd be shooting a lot more only paper, from prone or a bench with a serious rest instead of a rickety-ass cattle gate or rock, etc and would be jumping less than 10 thou, not 100 thou.

That said, while I'm not a fan of a lot of the mythology and "legacy theories" surrounding load development and reloading, please don't take that as me not being fully OCD and nerding out for the sake of making better ammo. I mean, I've got a table in my garage with a wet tumbling setup, 2 dry tumbling setups, and an ultrasonic cleaner, and I use different "recipes" of each depending on what I'm loading or what I'm doing because some are better tools depending on the job, so there's that... If I was trying to take the easy way out, I'm failing lol.

Load development for me means no nodes, no OCW, I pick a speed and only shoot as many as it takes to find out how many grains of powder I need to get the speed I'm looking for (usually I pick the middle of the book min-max and start there). Once I've got my speed/charge I move to seating depth and I usually shoot 50rds: 5 groups of 5, round-robin (letting the barrel cool between strings) at .040", .060", .080", .100", and .120" off the lands (25rds). From there I can usually see the best "jump zone" and I will narrow it down a little more from there if I need to. The last 25 of the 50 I've allocated for this usually leave me with enough to know I'm on something that works, with most of those ending up as "confirmation rounds" to gain some confidence in what I've got. Since I jump a bunch, my throat doesn't erode as fast, so I'm just looking for a 10-20 thou band I can park at the front of so my barrel never really changes much over its whole boring (hopefully long) life.

That's just what I do, not law, sometimes people forget that which is why some of the old BS keeps getting perpetuated I think.

If I was shooting F-Class, I'd probably be looking for a 6-9 thou band for my seating depth, and I'd expect ~half the life out of a barrel.

 

[Cfshooter]

IDK, sometimes it is, sometimes it isn't... usually, it's the monkey pulling the trigger who fucks things up, not the gun/load IME lol.

IMHO I think 1/2 MOA is fair in so far as what most of us can expect on the regular if we're using good/proven components (both rifle and reloading-wise) and put some work into stepping up our reloading game. FWIW, I come from the point of view that I'd rather 1/2 MOA always, over 1/4 MOA if I keep it in tune and nearly jam it... I want that extra ~1000rds or so of barrel life out of a barrel and I'm more after consistency/repeatability that I don't have to really think about again once load development is done. If I shot F-Class, I'd think about it and approach it differently since I'd be shooting a lot more only paper, from prone or a bench with a serious rest instead of a rickety-ass cattle gate or rock, etc and would be jumping less than 10 thou, not 100 thou.

That said, while I'm not a fan of a lot of the mythology and "legacy theories" surrounding load development and reloading, please don't take that as me not being fully OCD and nerding out for the sake of making better ammo. I mean, I've got a table in my garage with a wet tumbling setup, 2 dry tumbling setups, and an ultrasonic cleaner, and I use different "recipes" of each depending on what I'm loading or what I'm doing because some are better tools depending on the job, so there's that... If I was trying to take the easy way out, I'm failing lol.

Load development for me means no nodes, no OCW, I pick a speed and only shoot as many as it takes to find out how many grains of powder I need to get the speed I'm looking for (usually I pick the middle of the book min-max and start there). Once I've got my speed/charge I move to seating depth and I usually shoot 50rds: 5 groups of 5, round-robin (letting the barrel cool between strings) at .040", .060", .080", .100", and .120" off the lands (25rds). From there I can usually see the best "jump zone" and I will narrow it down a little more from there if I need to. The last 25 of the 50 I've allocated for this usually leave me with enough to know I'm on something that works, with most of those ending up as "confirmation rounds" to gain some confidence in what I've got. Since I jump a bunch, my throat doesn't erode as fast, so I'm just looking for a 10-20 thou band I can park at the front of so my barrel never really changes much over its whole boring (hopefully long) life.

That's just what I do, not law, sometimes people forget that which is why some of the old BS keeps getting perpetuated I think.

If I was shooting F-Class, I'd probably be looking for a 6-9 thou band for my seating depth, and I'd expect ~half the life out of a barrel.

Are you always able to get the speed you pick to shoot well?

 

[CK1.0]

Are you always able to get the speed you pick to shoot well?

Yes.

But I don't try to reinvent the wheel either.... these days I'm solidly in the "slower but fast enough" crowd (in 6CM I'm looking for ~2900fps, not 3100fps).

In fact, I like to land on a nice even/odd number (no decibel place) so it's easier to remember and monitor when loading... so if it ends up being a choice between, say 40.9gn or 41.2gn... I'm going with 41gn every time lol.

ETA: I haven't mentioned it, but like everyone else, I put at least 150-200 rounds through a barrel before I start any real/legit load development because the barrel needs to have stopped speeding up. But, towards the end of those "seasoning rounds", I'm already using them to look at my speed and seating depth to make an educated guess as to where to start or even where my load might end up. Because sometimes you get lucky and that's all it takes.

Like with my current barrel, I started with my old barrel's load since they were the same thing (Proof prefits) and I was going to be using the same case/primer/powder/bullet, and that ended up being it...

Zero load development, "picked a speed" (old load), 5 shots at 1250 yards (literally rounds #96-100 down the barrel), rear bag + bipod off the bench, didn't have to change shit:

 

[Cfshooter]

Yes.

But I don't try to reinvent the wheel either.... these days I'm solidly in the "slower but fast enough" crowd (in 6CM I'm looking for ~2900fps, not 3100fps).

In fact, I like to land on a nice even/odd number (no decibel place) so it's easier to remember and monitor when loading... so if it ends up being a choice between, say 40.9gn or 41.2gn... I'm going with 41gn every time lol.

ETA: I haven't mentioned it, but like everyone else, I put at least 150-200 rounds through a barrel before I start any real/legit load development because the barrel needs to have stopped speeding up. But, towards the end of those "seasoning rounds", I'm already using them to look at my speed and seating depth to make an educated guess as to where to start or even where my load might end up. Because sometimes you get lucky and that's all it takes.

Like with my current barrel, I started with my old barrel's load since they were the same thing (Proof prefits) and I was going to be using the same case/primer/powder/bullet, and that ended up being it...

Zero load development, "picked a speed" (old load), 5 shots at 1250 yards (literally rounds #96-100 down the barrel), rear bag + bipod off the bench, didn't have to change shit:

View attachment 8047186View attachment 8047187

Sometimes you get lucky, even more so when you use good components and have a good barrel. I lucked into 2 loads recently without any development. Once was another rifles load I used because I had some loaded up and it created a nice 3/4 moa 20 shot group, and the other was just a light charge thrown with a Lee PPM to break in a barrel and some brass that ended up putting up sun .5 moa 15 shot group (profile pic).

 

[Baron23]

What do you use to overlay groups, is it some type of program? I t
Do it with more of a photo program and it isn’t the best, hard to see all shots clearly after about 3 targets.

On Target’s TDS product (their more advanced and expensive package) says it will aggregate multiple POA.

I use the cheaper product so I have no direct experience with this feature.

OnTarget TDS - Analyzes target info and generates advanced statistics

OnTarget TDS - Includes automated target analysis, group statistics including SD and CEP, and virtual groups for calculating stats using higher shot counts.

ontargetshooting.com

 

[Tokay444]

I really don't want to get too crazy going back and forth about this, but since @Baron23 pretty much hit the nail on the head...

I am sorry if I didn't satisfy the minutia before by not mentioning POI (only mentioning MV), but yeah, that part of the OCW nonsense is BS too.

This is as simple as: cause = effect. We're talking combustion... more fuel (powder) = more something.

More fuel = more MV. More fuel = POI shift too. If you don't see a change in POI, it just means you haven't shot enough rounds to see what you think you see.

I think it's ridiculous to keep acting like the laws of physics don't apply to reloading ammo, even when, besides it obviously makes no common sense whatsoever, people with degrees in this shit tell you why (statistics per Hornady engineer).

Telling others to keep working on the same fool's errand when components are so expensive and scarce is damn near mean.

The Hornady engineers preface their whole discussion by saying, “this is for steel shooters”.

 

[bax]

I started reading the thread early. At first I was "ho hum, good stuff but same old stuff". Then people started talking about OCW and I thought (feeling superior), "I'm smart, I know what these guys are talking about". Then some wild man comes in and says that all our children are ugly and I'm pissed! Then I keep reading and I discover that some people try to choose a configuration by looking at velocities on their chronograph and some other people are looking at their targets. I'm confused - what are y'all doing?

I'm in that second bunch. I shoot 3-shot groups where each 3-shot group has the same charge. The loading block has maybe ten rows of cases and there is an increased charge from one row to the next - the delta depends on the case size and powder. I am looking for groups that are round and where three consecutive rows impact in about the same place. I stop when I see pressure. When I find one or two sets like that, I reshoot the same three rows to see if it repeats - mostly they do but not always. If it does repeat, I increase the charge range a little (I want to make sure that I identify the bottom and top end of the sweet spot) and reduce the charge increment to 0.1 grain and reshoot. I now have good gun data from that load and from there I usually pick a charge in the middle of the range and load that. I do not use a chronograph. When I have a load that shoots, I shoot it from 100 out to as far as I can go, writing down the ups. I open Applied Ballistics, configure the cartridge then change the velocity until AB predicts the curve I just measured.

Last weekend, I shot 25 rounds at 1k. When the barrel was new, AB told me that the velocity was 2700 fps and telling me to dial 7.6 for 1k. This has been a good setting for about 200 rounds. But last Sunday I had to dial 7.3 in order for my point of aim to match my point of impact. Apparently something changed and the velocity increased by about 55 fps. I don't KNOW that the velocity changed but that it what it takes to make hits so that is what I use.

It has not occurred to me that I should try to find three different charges that gave about the same velocity. I stopped caring about SD and ES a long time ago - I could never get it to relate to group size so I stopped caring about those numbers. I do care about the average velocity number so I can dial or hold but I don't care what the number is, it is just a parameter in the function that gives me "ups" and windage.

YMMV

 

[RegionRat]

Last weekend, I shot 25 rounds at 1k. When the barrel was new, AB told me that the velocity was 2700 fps and telling me to dial 7.6 for 1k. This has been a good setting for about 200 rounds. But last Sunday I had to dial 7.3 in order for my point of aim to match my point of impact. Apparently something changed and the velocity increased by about 55 fps. I don't KNOW that the velocity changed but that it what it takes to make hits so that is what I use.

It doesn't take an extraordinary Density Altitude change to explain a 0.3 Mil dope change at 1000 yards with a 2700 FPS muzzle velocity.
It would have been good to have the muzzle velocity to know for sure, but that isn't a very large shift at 1000 yards at all.

 

[bax]

It doesn't take an extraordinary Density Altitude change to explain a 0.3 Mil dope change at 1000 yards with a 2700 FPS muzzle velocity.
It would have been good to have the muzzle velocity to know for sure, but that isn't a very large shift at 1000 yards at all.

I have Kestrel instrumentation and I use it. At the beginning of todays session, conditions were 29.10 inHg absolute, 34F and 54% rh. That works out to 7.5 mils. After five warmup shots, my scope was set to 7.4 and I was getting center hits. If I change the AB temperature to 14F (that is 20F colder) the computation says 7.6 - denser air, more drop. If I change the temperature to 54F (20 degrees warmer) the computation says 7.4 - warmer air is less dense, should hit higher. Three tenths is a lot - that is 10.8 inches on the target and requires a big temperature swing. By the end of the session, I may have warmed up to 38 but no more than that.

 

[morganlamprecht]

It’s common for barrels to speed up in the first 100-300 rounds when new…when it happens in that range just depends on the barrel

 

[Tempest 455]

Wont get into argument on nodes.

However, have won two state F class long range championships at 1,000 yards and many regional ones using OCW testing. I do mine at 600 yards. If done right it clearly illustrates a node at a specific temp, velocity, pressure, elevation etc. You can clearly see where some nodes scatter like a shotgun and some are like a F'ing laser. This is on an F class gun with 32" barrel.

That being said. I also have seen where every barrel is different and may not show much of a difference. Also have seen where doing OCW with a suppressor showed do change at all.

 

[howler]

Wont get into argument on nodes.

However, have won two state F class long range championships at 1,000 yards and many regional ones using OCW testing. I do mine at 600 yards. If done right it clearly illustrates a node at a specific temp, velocity, pressure, elevation etc. You can clearly see where some nodes scatter like a shotgun and some are like a F'ing laser. This is on an F class gun with 32" barrel.

That being said. I also have seen where every barrel is different and may not show much of a difference. Also have seen where doing OCW with a suppressor showed do change at all.

Playing devil’s advocate, do you really think the OCW test was a key component of your wins? Who’s to say that it’s not all the other meticulous steps, and the OCW tests didn’t really make any measurable difference?

Also, have you done repeated OCW tests to confirm that these nodes are indeed real/repeatable and not a product of small sampling size and confirmation bias?

I would say you won those competitions because you worked your ass off practicing and refining your craft, not because of a pseudo scientific method. But that’s just my opinion.

 

[Tempest 455]

Playing devil’s advocate, do you really think the OCW test was a key component of your wins? Who’s to say that it’s not all the other meticulous steps, and the OCW tests didn’t really make any measurable difference?

Also, have you done repeated OCW tests to confirm that these nodes are indeed real/repeatable and not a product of small sampling size and confirmation bias?

I would say you won those competitions because you worked your ass off practicing and refining your craft, not because of a pseudo scientific method. But that’s just my opinion.

All the above:

But as I said, my testing and results were/are clear with "my barrel". I could see for example where 43.6 grains on "my barrel" at 50F was a shotgun, where 44.4 was a laser. At 80F it may not have been again. Then I test again.

Barrels are like kids, everyone is different. And need to be tested in various conditions. They are all different.

I've learned, if you think you tested everything, there are others that tested more!

 

[CK1.0]

All the above:

But as I said, my testing and results were/are clear with "my barrel". I could see for example where 43.6 grains on "my barrel" at 50F was a shotgun, where 44.4 was a laser. At 80F it may not have been again. Then I test again.

Barrels are like kids, everyone is different. And need to be tested in various conditions. They are all different.

I've learned, if you think you tested everything, there are others that tested more!

What you are describing is called "combustion", not "finding a node". Combustion is affected by ambient temperature, a lot (which is most of the reason why we all try to use the most temp-insensitive powders we can).

There are like a million boring articles on it out there if you want to wade out into the weeds... but it gets deep fast lol:

https://www.sciencedirect.com/science/article/abs/pii/S0360544218315986

There are always going to be some charges that are going to work better than others at different ambient temperatures, but you could shoot a whole barrel out testing it and still might not be able to nail down a completely repeatable pattern.

You can burn up your components testing if you want, but it's more than likely the "node" you found with 44.4gn at 50degF doesn't exist at 80degF, and if it did show up miraculously, again, you could shoot the barrel out trying to prove it, and that might not even be enough to show it wasn't a fluke/coincidence.

I'd bet you won those matches because of all the other stuff that goes into winning matches... at least that's what I'd put my money on.

 

[Doom]

Going back to the discussion on statistics and sample size too many are misunderstanding the point that Hornady and Kieth Glasscock make in its application of testing. In the real world where we test for applications to either modify production, testing for damages related to performance of equipment, or designing a test to determine the effect of a change in some variable, we have to consider the sample size to ensure that the results have the desired confidence. The confidence required determines the sample size of the test.

One of the worst examples of testing was Scott Satterlee's one shot ladder. The following is attributed to Scott from the 6.5 Guy's site

“I start 1.5 grains below my max load and load 10 shells ascending by .2 gr. So for the Swedemoor, 50.0, .2, .4, .6, .8, 51.0, .2, .4, .6, .8, 52.0
Then I will shoot these over the chronograph and look for the nodes. A node will be a velocity flat spot where .4-.8 gr of powder doesn’t move the speedometer much. This example with Reloader 26 in my 6.5 Addiction with 140 RDFs, the flat spot is between 51.2 and 51.8 grains -velocity went from 3025-3033 fps. So, .8 grains of powder added a total of 8 fps. Therefore, the middle of my node is 51.5 grains."

In this example with .2 grain increments he was expecting to find velocities that varied by 6 fps or less with an instrument with an accuracy of +/- 3fps and to find it with one shot when loading a round which will have a standard deviation greater than 5 fps. Statistically detecting what he intended was impossible. There is too much uncertainty to find the perceived flat spot.

We can shoot 3 shot groups with a chronograph and the average will be somewhere in the ballpark of the true average but the standard deviation is a crap shoot. Making a decision on whether we are at a velocity we need is probably OK but thinking that the standard deviation is meaningful is "BS". Using that mean velocity for ELR will likely be incorrect and its likely we will blame the ballistic coefficient when the error is likely to be in the velocity or zero, depending on how we have determined these values.

Similarly we can shoot a three shot group for zeroing and it will get us close or it might get us spot on but we really don't know. Often we may actually attribute a zero error to scope drift when in reality it lies in the uncertainty of the zero due to a small sample size. Insufficient data leads to a probable wrong conclusion in this case.

If we are evaluating consistency of our reloads then we are trying to understand the standard deviation. By definition the standard deviation does not fit a normal distribution like the mean (average). it is bounded by zero on the low side and it fits what is called a Chi-Squared distribution. To develop confidence in the standard deviation it takes a significant number of shots. When someone says they have a standard deviation of 8 fps that number has a confidence interval associated with it. For 3 shots that range is 4 to 50 fps. For 5 shots its 5 to 23 fps. For 10 shots 5.5 to 14.6, and for 20 shots it's 6 to 11.6 fps. If the reloader was looking for single digit standard deviation for his handholds he would be very unlikely to have it from the 3, 5, or even a 10 shot group. Even with the 20 shot group there is only a 75% confidence interval. This means that if an infinite number of 20 test were done on 75% of them would be in the range of 6 to 10 fps. This type of behavior would also apply to the standard deviation of the various radii in a group for determining mean radius.

SO DO NODES EXIST OR NOT?

There is a lot of "data" and analysis that seems to indicate that "nodes" exist in some form. Seating nodes, powder nodes and maybe primer nodes? There is is also mounting evidence that nodes per se don't exists. I have seen OCW tests on rifles where the POI did not move of a significant range of powder loads. I also know that my 223 and 308 show a definite "node" for a given seating depth. The OCW method usually depends on 9 shots to show what we refer to as a "node" with 3 different charge weights. As an engineer, I know that barrels vibrate and it can show up on target. That is a fact. Heavy barrels will vibrate with a smaller amplitude than lighter barrels, hence less effect on POI. I'll take that as gospel. I cannot put together a theory as to why a small change in powder charge in a reasonably full case would yield a significant change in velocity standard deviation. Do seating nodes exist? There is a test that is published on the subject on the Precision Rifle Blog that shows a definite defendable correlation, at lest for the bullets and barrels tested.

My personal untested, unverified opinion is I believe that nodes exist for barrel vibration that is more pronounced in thinner, lighter weight barrels and that changes in seating depth and powder charge will affect this. I also believe that for a given powder charge there is a seating depth that will find the barrel node. That is, the node concept does exist but our interpretation of it is likely in error, and one of the sources of that error is too small of sample sizes.

This may be similar to the proverbial question in physics, is it particle or wave? And the answer turned out to be Yes!

 

[CK1.0]

Going back to the discussion on statistics and sample size too many are misunderstanding the point that Hornady and Kieth Glasscock make in its application of testing. In the real world where we test for applications to either modify production, testing for damages related to performance of equipment, or designing a test to determine the effect of a change in some variable, we have to consider the sample size to ensure that the results have the desired confidence. The confidence required determines the sample size of the test.

One of the worst examples of testing was Scott Satterlee's one shot ladder. The following is attributed to Scott from the 6.5 Guy's site

“I start 1.5 grains below my max load and load 10 shells ascending by .2 gr. So for the Swedemoor, 50.0, .2, .4, .6, .8, 51.0, .2, .4, .6, .8, 52.0
Then I will shoot these over the chronograph and look for the nodes. A node will be a velocity flat spot where .4-.8 gr of powder doesn’t move the speedometer much. This example with Reloader 26 in my 6.5 Addiction with 140 RDFs, the flat spot is between 51.2 and 51.8 grains -velocity went from 3025-3033 fps. So, .8 grains of powder added a total of 8 fps. Therefore, the middle of my node is 51.5 grains."

In this example with .2 grain increments he was expecting to find velocities that varied by 6 fps or less with an instrument with an accuracy of +/- 3fps and to find it with one shot when loading a round which will have a standard deviation greater than 5 fps. Statistically detecting what he intended was impossible. There is too much uncertainty to find the perceived flat spot.

We can shoot 3 shot groups with a chronograph and the average will be somewhere in the ballpark of the true average but the standard deviation is a crap shoot. Making a decision on whether we are at a velocity we need is probably OK but thinking that the standard deviation is meaningful is "BS". Using that mean velocity for ELR will likely be incorrect and its likely we will blame the ballistic coefficient when the error is likely to be in the velocity or zero, depending on how we have determined these values.

Similarly we can shoot a three shot group for zeroing and it will get us close or it might get us spot on but we really don't know. Often we may actually attribute a zero error to scope drift when in reality it lies in the uncertainty of the zero due to a small sample size. Insufficient data leads to a probable wrong conclusion in this case.

If we are evaluating consistency of our reloads then we are trying to understand the standard deviation. By definition the standard deviation does not fit a normal distribution like the mean (average). it is bounded by zero on the low side and it fits what is called a Chi-Squared distribution. To develop confidence in the standard deviation it takes a significant number of shots. When someone says they have a standard deviation of 8 fps that number has a confidence interval associated with it. For 3 shots that range is 4 to 50 fps. For 5 shots its 5 to 23 fps. For 10 shots 5.5 to 14.6, and for 20 shots it's 6 to 11.6 fps. If the reloader was looking for single digit standard deviation for his handholds he would be very unlikely to have it from the 3, 5, or even a 10 shot group. Even with the 20 shot group there is only a 75% confidence interval. This means that if an infinite number of 20 test were done on 75% of them would be in the range of 6 to 10 fps. This type of behavior would also apply to the standard deviation of the various radii in a group for determining mean radius.

SO DO NODES EXIST OR NOT?

There is a lot of "data" and analysis that seems to indicate that "nodes" exist in some form. Seating nodes, powder nodes and maybe primer nodes? There is is also mounting evidence that nodes per se don't exists. I have seen OCW tests on rifles where the POI did not move of a significant range of powder loads. I also know that my 223 and 308 show a definite "node" for a given seating depth. The OCW method usually depends on 9 shots to show what we refer to as a "node" with 3 different charge weights. As an engineer, I know that barrels vibrate and it can show up on target. That is a fact. Heavy barrels will vibrate with a smaller amplitude than lighter barrels, hence less effect on POI. I'll take that as gospel. I cannot put together a theory as to why a small change in powder charge in a reasonably full case would yield a significant change in velocity standard deviation. Do seating nodes exist? There is a test that is published on the subject on the Precision Rifle Blog that shows a definite defendable correlation, at lest for the bullets and barrels tested.

My personal untested, unverified opinion is I believe that nodes exist for barrel vibration that is more pronounced in thinner, lighter weight barrels and that changes in seating depth and powder charge will affect this. I also believe that for a given powder charge there is a seating depth that will find the barrel node. That is, the node concept does exist but our interpretation of it is likely in error, and one of the sources of that error is too small of sample sizes.

This may be similar to the proverbial question in physics, is it particle or wave? And the answer turned out to be Yes!

I agree that there does seem to be some correlation to seating depth that some guys will call a "node" (I prefer to just call it "a good seating depth for my particular barrel/load" lol).

I feel like out of all the load development stuff guys may or may not do, seating depth is probably the easiest thing to wrap one's head around and likely the most important thing we can do to find a good load. I feel that way, mostly, because that's one of the few things that gets discussed that is actually repeatable over multiple barrels and with multiple different cartridges. It's also not as easily explained away due to changes in ambient temperature being tied to varying combustion performance, and the elephant in the room, using good old statistics.

Experimenting with seating depth was and still is the original "barrel tuner" on the scene. Transients, harmonics, frequency, and amplitude exist in the known world, no impossible-to-explain pseudo-physics theories are needed.

(As an aside, not to start a separate controversy, but I got a weird reaction the other day from a guy at the range after saying I didn't want a tuner on my gun. I said: "For rimfire, sure, I get it, you need to tune the gun to the ammo for that. But not on my centerfires, because I mainly shoot my own shit and I've already got a room at home full of thousands of dollars of reloading shit for that" hahaha.)

I feel like most of the nonsense that keeps getting perpetuated comes from plain old Bubba-logic: the old "that's the way we've always done it" mantra. The rest of it maybe comes from those who've been doing it a certain way for so long that they ignore that they are emotionally vested in it being true (afraid to admit they're wrong), and they won't let it go no matter how many statistics and facts are brought to bear. People believed the earth was flat too for a long time (and some dumbasses still do).

The truth of the matter is, if a guy decides on a particular charge weight over another and keeps loading that charge as repeatably and consistently as possible, they're going to get repeatable and consistent results.

If thinking they've "found a node" or an "optimum charge weight" makes them feel better or gives them confidence... then so be it. But, whether one calls it confirmation bias, a Rorschach test, or something else (bullshit), any of those are fine and apply because that's what it is.

Going forward, to those who say it, please stop being ridiculous and calling it a "node" or "optimum charge weight", because statistics and physics don't back that up.

Instead, when a new guy gets on the forum and posts why he can't find a node or why his OCW test didn't go as planned, etc... the comments should begin with something closer to, IDK, maybe "decide on a charge weight and buy the best scale you can afford" rather than all this other nonsense...

 

[straightshooter1]

As an engineer, I know that barrels vibrate and it can show up on target. That is a fact. Heavy barrels will vibrate with a smaller amplitude than lighter barrels, hence less effect on POI.

Wouldn't you say heavy barrels vibrate at a different "frequency" than lighter barrels?

My understanding is that a particular barrel will have its frequency and the amplitude of that frequency can change depending on how much energy is imparted onto it while the frequency is the same. Take a barrel and tap it with a rubber mallet and listen to the frequency. Hit it harder and you can hear the higher amplitude (that it's louder, but with the same sound/frequency). In terms of various frequencies only, various frequencies can have the same amplitude. Apply the same energy to two things that will have a different frequency and the amplitude with also change, like amplitude will become smaller when the frequency increases.

. . . or am I just not understanding harmonics?

 

[Doom]

Wouldn't you say heavy barrels vibrate at a different "frequency" than lighter barrels?

My understanding is that a particular barrel will have its frequency and the amplitude of that frequency can change depending on how much energy is imparted onto it while the frequency is the same. Take a barrel and tap it with a rubber mallet and listen to the frequency. Hit it harder and you can hear the higher amplitude (that it's louder, but with the same sound/frequency). In terms of various frequencies only, various frequencies can have the same amplitude. Apply the same energy to two things that will have a different frequency and the amplitude with also change, like amplitude will become smaller when the frequency increases.

. . . or am I just not understanding harmonics?

The natural frequency is related by the square root of k (related to stiffness, Youngs Modulus) divided by weight so the greater the mass the lower the frequency (slower) for the same length. The magnitude and frequency are also a function of length. Longer barrels vibrate slower than the same weight shorter barrels. The magnitude (amplitude) is a function of the force but the frequency is not. This refers to translational vibration, the vertical and horizontal movement of the barrel. You can look up beam vibration to research this. The vibration that Chris Long refers to in his work is acoustical in nature and a different beast.

 

[bax]

The truth of the matter is, if a guy decides on a particular charge weight over another and keeps loading that charge as repeatably and consistently as possible, they're going to get repeatable and consistent results.

Let me ask a question. I know that the optimum charge weight for my brass and bullets in two of my guns is 41.52 grains of IMR 4064. If I change the charge to 41.7 or 41.3, the groups will be larger, actually much larger. Are you saying that I can shoot any charge weight I want and get good groups? Can I drop the charge weight to 20 grains and save money?

 

[howler]

nope, and you’re not proving anything with ridiculous suggestions. You pick the powder charge that achieves the velocity that you want (safely), and then you work on seating depth from there (assuming your sizing process is good). If you can’t get your loads to shoot because you’re .01 grains off a made up node, then I’m afraid you have bigger issues.

 

[straightshooter1]

The natural frequency is related by the square root of k (related to stiffness, Youngs Modulus) divided by weight so the greater the mass the lower the frequency (slower) for the same length. The magnitude and frequency are also a function of length. Longer barrels vibrate slower than the same weight shorter barrels. The magnitude (amplitude) is a function of the force but the frequency is not. This refers to translational vibration, the vertical and horizontal movement of the barrel. You can look up beam vibration to research this. The vibration that Chris Long refers to in his work is acoustical in nature and a different beast.

Thanks for your response. And yes, I understand and agree with all that. It was just your emphasis on amplitude being smaller on heavy barrels than lighter barrels that struck me as it seems the difference in frequency between a heavy barrel and a lighter barrel is what's key in the harmonic timing. A longer frequency, as heavy barrels will have, makes for a longer "node" than lighter barrels are harder to zero in on a charge weight that produces consistent small groups. As far as amplitude goes, if a larger charge creates a larger amplitude on a particular barrel than a previous charge, the frequency remains the same but the period of the anti-node of the sine wave is shorter, isn't it?

 

[918v]

You pick the powder charge that achieves the velocity that you want (safely), and then you work on seating depth from there (assuming your sizing process is good).

And what do you do when you can’t seat the bullet any deeper?

 

[howler]

And what do you do when you can’t seat the bullet any deeper?

Contact your gunsmith and tell them you messed up and didn’t get enough freebore? The lands only grow farther away as they erode. If your bullet doesn’t fit, that’s a chambering issue.

 

[918v]

Lol

 

[Tempest 455]

What you are describing is called "combustion", not "finding a node". Combustion is affected by ambient temperature, a lot (which is most of the reason why we all try to use the most temp-insensitive powders we can).

There are like a million boring articles on it out there if you want to wade out into the weeds... but it gets deep fast lol:

https://www.sciencedirect.com/science/article/abs/pii/S0360544218315986

There are always going to be some charges that are going to work better than others at different ambient temperatures, but you could shoot a whole barrel out testing it and still might not be able to nail down a completely repeatable pattern.

You can burn up your components testing if you want, but it's more than likely the "node" you found with 44.4gn at 50degF doesn't exist at 80degF, and if it did show up miraculously, again, you could shoot the barrel out trying to prove it, and that might not even be enough to show it wasn't a fluke/coincidence.

I'd bet you won those matches because of all the other stuff that goes into winning matches... at least that's what I'd put my money on.

What competitive class do you shoot?

 

[Doom]

Thanks for your response. And yes, I understand and agree with all that. It was just your emphasis on amplitude being smaller on heavy barrels than lighter barrels that struck me as it seems the difference in frequency between a heavy barrel and a lighter barrel is what's key in the harmonic timing. A longer frequency, as heavy barrels will have, makes for a longer "node" than lighter barrels are harder to zero in on a charge weight that produces consistent small groups. As far as amplitude goes, if a larger charge creates a larger amplitude on a particular barrel than a previous charge, the frequency remains the same but the period of the anti-node of the sine wave is shorter, isn't it?

Yes.

 

[bax]

nope, and you’re not proving anything with ridiculous suggestions. You pick the powder charge that achieves the velocity that you want (safely), and then you work on seating depth from there (assuming your sizing process is good). If you can’t get your loads to shoot because you’re .01 grains off a made up node, then I’m afraid you have bigger issues.

FWIW, my load tolerance is plus or minus 0.02 grains - that is, 41.50 to 41.54. I think that 41.48 to 41.56 is still okay. I can probably go 41.47 to 41.57 with some reduction in accuracy but I can reliably do plus or minus 0.02 and it works for me so that is what I do.

Suppose I say that I want 2700 fps, with 175 grain SMK bullets. I can demonstrate that, in my rifles, a 2700 fps load won't shoot well where a 41.52 grain load will shoot well. In my rifles, 41.52 grains gives the best accuracy with good brass life. I honestly do not know the velocity and I do not care. I care about accuracy. Adding powder to hit some arbitrary velocity number while ignoring the accuracy is silly - there is nothing magic about 2700 fps. There are probably several (3 maybe 4) velocities that will shoot well in my rifles but there are many many more powder charges and corresponding velocities (and barrel times) that will shoot poorly.

For a given powder charge, bullet, case, and primer - you get different barrel times. The speed of sound in steel is about 18,000 fps. Gordon's says that my 308 load in a 26-inch barrel has a 1.35 millisecond barrel time. During 1.35 milliseconds, the shock wave created by ignition has traveled from the breech to the muzzle and back about five and a half times - the muzzle end of that barrel is waving around like an beer-chugging Irish setter's tail. The barrel is getting longer and shorter, it is twisting and untwisting, and it is swinging vertically and horizontally - all at the same time.

Imagine that you are looking at the muzzle end of the barrel from the side. Suppose that the barrel is resonating only up and down (it is much more complex that that). This is a chart of the direction the barrel is pointing over one full cycle - pointing center, pointing up, passing back through center, pointing down, then going back to center.

I want to bullet exit at the red arrow points

The objective is to have the bullet exit the barrel at the end of a swing. Not in the middle when the barrel direction is pointing straight ahead. Why? Because at the end of a swing the muzzle end of the barrel has to decelerate, stop, then accelerate back in the other direction. I want to bullet to leave when the barrel stops swinging. Apparently, in my rifle, at 1.35 milliseconds from ignition, the barrel is approximately at the end of a swing and, for each shot, pointing in about the same direction so I get good groups.

If I add powder, the barrel time drops to say 1.30 milliseconds - 50 microseconds sooner. At that time, the barrel may be right in the middle of the swing. In the middle of the swing, the barrel direction changes the fastest so even tiny differences in barrel time cause bigger groups - notice the slope of the line around 11 on the chart. At the end of the swing, the barrel direction changes slowly or actually stops for an instant. I think that if the bullet leaves the barrel when it stops swinging, I get the best groups. So the trick is to find the powder charge that creates a barrel time that matches when the barrel motion is at a minimum. I do that with ladders.

Laugh if you want but that's my theory, it works for me, and I'm sticking to it

 

[morganlamprecht]

You are one bad mf’er to shoot the difference in +/- .02 gr lol

 

[bax]

https://www.sciencedirect.com/science/article/abs/pii/S0360544218315986

Let's check your reference here. This article is about ignition probability of micron-sized aluminum powder in an oxidizing substrate used as fuel in a solid rocket motors evaluated over a 300K temperature range - more or less 540 degrees F. Over that temperature range probability of ignition changes by a factor of 6.7. Their aluminum particle size range is 40 to 170 micrometers. A sheet of paper is about 180 micrometers thick - this is MUCH smaller than smokeless powder grains. For all intents and purposes they are evaluating a substance commonly called flash - used in firecrackers and pyrotechnics.

With ammunition we have rounds at temperature ~70F placed into a chamber, inside a brass case, that is ~110F - a 40 F range. Smokeless powder is one or two orders of magnitude larger than the aluminum in the document. Smokeless is a wholly different composition. When the firing pin drops, there is never any question that the powder will ignite.

There is some comparison - their testing and shooting are both about combustion - but I need to see some calibration between the materials and conditions before I would apply any of their observations to shooting. This seems a huge stretch.

 

[bax]

You are one bad mf’er to shoot the difference in +/- .02 gr lol

my point - there is no difference between 41.50 and 41.54. But as the range increases to say 41.47 to 41.57 groups get bigger. I use a Sartorius scale it is equivalent to the scale that most Autothrow people use.

 

[morganlamprecht]

O I was clear on the point you were tryin to make

 

[howler]

FWIW, my load tolerance is plus or minus 0.02 grains - that is, 41.50 to 41.54. I think that 41.48 to 41.56 is still okay. I can probably go 41.47 to 41.57 with some reduction in accuracy but I can reliably do plus or minus 0.02 and it works for me so that is what I do.

Suppose I say that I want 2700 fps, with 175 grain SMK bullets. I can demonstrate that, in my rifles, a 2700 fps load won't shoot well where a 41.52 grain load will shoot well. In my rifles, 41.52 grains gives the best accuracy with good brass life. I honestly do not know the velocity and I do not care. I care about accuracy. Adding powder to hit some arbitrary velocity number while ignoring the accuracy is silly - there is nothing magic about 2700 fps. There are probably several (3 maybe 4) velocities that will shoot well in my rifles but there are many many more powder charges and corresponding velocities (and barrel times) that will shoot poorly.

For a given powder charge, bullet, case, and primer - you get different barrel times. The speed of sound in steel is about 18,000 fps. Gordon's says that my 308 load in a 26-inch barrel has a 1.35 millisecond barrel time. During 1.35 milliseconds, the shock wave created by ignition has traveled from the breech to the muzzle and back about five and a half times - the muzzle end of that barrel is waving around like an beer-chugging Irish setter's tail. The barrel is getting longer and shorter, it is twisting and untwisting, and it is swinging vertically and horizontally - all at the same time.

Imagine that you are looking at the muzzle end of the barrel from the side. Suppose that the barrel is resonating only up and down (it is much more complex that that). This is a chart of the direction the barrel is pointing over one full cycle - pointing center, pointing up, passing back through center, pointing down, then going back to center.
View attachment 8050541
I want to bullet exit at the red arrow points

The objective is to have the bullet exit the barrel at the end of a swing. Not in the middle when the barrel direction is pointing straight ahead. Why? Because at the end of a swing the muzzle end of the barrel has to decelerate, stop, then accelerate back in the other direction. I want to bullet to leave when the barrel stops swinging. Apparently, in my rifle, at 1.35 milliseconds from ignition, the barrel is approximately at the end of a swing and, for each shot, pointing in about the same direction so I get good groups.

If I add powder, the barrel time drops to say 1.30 milliseconds - 50 microseconds sooner. At that time, the barrel may be right in the middle of the swing. In the middle of the swing, the barrel direction changes the fastest so even tiny differences in barrel time cause bigger groups - notice the slope of the line around 11 on the chart. At the end of the swing, the barrel direction changes slowly or actually stops for an instant. I think that if the bullet leaves the barrel when it stops swinging, I get the best groups. So the trick is to find the powder charge that creates a barrel time that matches when the barrel motion is at a minimum. I do that with ladders.

Laugh if you want but that's my theory, it works for me, and I'm sticking to it

Hard to argue with results, and differing opinions drives innovation. I’m always happy to have a chance to see a different perspective.

 

[Tempest 455]

Some good points on this topic. I don't care a rats ass about velocity either. I've slowed rounds down that became more accurate for given powder/bullet weight.

I care about accuracy. I care about a score. I care about a 10 or an X at long distances.

 

[Baron23]

The natural frequency is related by the square root of k (related to stiffness, Youngs Modulus) divided by weight so the greater the mass the lower the frequency (slower) for the same length. The magnitude and frequency are also a function of length. Longer barrels vibrate slower than the same weight shorter barrels. The magnitude (amplitude) is a function of the force but the frequency is not. This refers to translational vibration, the vertical and horizontal movement of the barrel. You can look up beam vibration to research this. The vibration that Chris Long refers to in his work is acoustical in nature and a different beast.

Perhaps you can answer me this one. It seems to me that most often we talk about "harmonics", "vibration", whatever as though the muzzle movement is a sine wave ONLY in the vertical axis. Isn't this the basis of "positive compensation"...that is, attempt to time the bullet's exit from the muzzle either at the top or bottom of the sine wave where the velocity will be lowest. Right?

I see zero reason why this should be. The barrel and chamber are round. If there is some sort of collapse of all possible movement into a single vector, then even then I don't see any reason for this to be in the vertical only.

And it seems that stuff like Newberry, OWC, and ladder tests in general (and I may be wrong about this) are only looking for minimal dispersion in the vertical axis when doing load development.

I'm sure I'm missing something and thought perhaps you could shed some light on this. I've brought this up in passing on SH before, but nobody has risen to the challenge of explaining it to my dumb ass.

 

[nn8734]

Perhaps you can answer me this one. It seems to me that most often we talk about "harmonics", "vibration", whatever as though the muzzle movement is a sine wave ONLY in the vertical axis. Isn't this the basis of "positive compensation"...that is, attempt to time the bullet's exit from the muzzle either at the top or bottom of the sine wave where the velocity will be lowest. Right?

I see zero reason why this should be. The barrel and chamber are round. If there is some sort of collapse of all possible movement into a single vector, then even then I don't see any reason for this to be in the vertical only.

And it seems that stuff like Newberry, OWC, and ladder tests in general (and I may be wrong about this) are only looking for minimal dispersion in the vertical axis when doing load development.

I'm sure I'm missing something and thought perhaps you could shed some light on this. I've brought this up in passing on SH before, but nobody has risen to the challenge of explaining it to my dumb ass.

OCW testing looks for shifts in the groups’ center-of-poi in any direction from the previous group at 100m.

A high performing load will have minimal vertical dispersion at all portions of the supersonic flight envelope when a capable platform is fired from a test fixture at a test target at whatever distance when an optimal charge and jump has been arrived at…

horizontal dispersion isn’t considered important when evaluating a load’s performance at distances greater than 200-300m because wind/atmospherics and spin drift are much more influential.

My .02

 

[straightshooter1]

FWIW, my load tolerance is plus or minus 0.02 grains - that is, 41.50 to 41.54. I think that 41.48 to 41.56 is still okay. I can probably go 41.47 to 41.57 with some reduction in accuracy but I can reliably do plus or minus 0.02 and it works for me so that is what I do.

Suppose I say that I want 2700 fps, with 175 grain SMK bullets. I can demonstrate that, in my rifles, a 2700 fps load won't shoot well where a 41.52 grain load will shoot well. In my rifles, 41.52 grains gives the best accuracy with good brass life. I honestly do not know the velocity and I do not care. I care about accuracy. Adding powder to hit some arbitrary velocity number while ignoring the accuracy is silly - there is nothing magic about 2700 fps. There are probably several (3 maybe 4) velocities that will shoot well in my rifles but there are many many more powder charges and corresponding velocities (and barrel times) that will shoot poorly.

For a given powder charge, bullet, case, and primer - you get different barrel times. The speed of sound in steel is about 18,000 fps. Gordon's says that my 308 load in a 26-inch barrel has a 1.35 millisecond barrel time. During 1.35 milliseconds, the shock wave created by ignition has traveled from the breech to the muzzle and back about five and a half times - the muzzle end of that barrel is waving around like an beer-chugging Irish setter's tail. The barrel is getting longer and shorter, it is twisting and untwisting, and it is swinging vertically and horizontally - all at the same time.

Imagine that you are looking at the muzzle end of the barrel from the side. Suppose that the barrel is resonating only up and down (it is much more complex that that). This is a chart of the direction the barrel is pointing over one full cycle - pointing center, pointing up, passing back through center, pointing down, then going back to center.
View attachment 8050541
I want to bullet exit at the red arrow points

The objective is to have the bullet exit the barrel at the end of a swing. Not in the middle when the barrel direction is pointing straight ahead. Why? Because at the end of a swing the muzzle end of the barrel has to decelerate, stop, then accelerate back in the other direction. I want to bullet to leave when the barrel stops swinging. Apparently, in my rifle, at 1.35 milliseconds from ignition, the barrel is approximately at the end of a swing and, for each shot, pointing in about the same direction so I get good groups.

If I add powder, the barrel time drops to say 1.30 milliseconds - 50 microseconds sooner. At that time, the barrel may be right in the middle of the swing. In the middle of the swing, the barrel direction changes the fastest so even tiny differences in barrel time cause bigger groups - notice the slope of the line around 11 on the chart. At the end of the swing, the barrel direction changes slowly or actually stops for an instant. I think that if the bullet leaves the barrel when it stops swinging, I get the best groups. So the trick is to find the powder charge that creates a barrel time that matches when the barrel motion is at a minimum. I do that with ladders.

Laugh if you want but that's my theory, it works for me, and I'm sticking to it

As I pretty much agree with all that you're saying, ideally we want the bullet to leave when the barrel stops at the anti-node of that wave. But, that would require each shot to have exactly the same velocity . . . and a lot of effort to find the exact timing. So, to be clear, we're trying to get as close to that as possible within a period of that time at the apex of the anti-node (like I indicate with the two arrows). The flatter the wave, the flatter that area . . . which is one of the reasons why heavy long barrels with their lower frequency makes it easier to tune a load than light thin barrels.

 

[Evintos]

Perhaps you can answer me this one. It seems to me that most often we talk about "harmonics", "vibration", whatever as though the muzzle movement is a sine wave ONLY in the vertical axis. Isn't this the basis of "positive compensation"...that is, attempt to time the bullet's exit from the muzzle either at the top or bottom of the sine wave where the velocity will be lowest. Right?

I see zero reason why this should be. The barrel and chamber are round. If there is some sort of collapse of all possible movement into a single vector, then even then I don't see any reason for this to be in the vertical only.

And it seems that stuff like Newberry, OWC, and ladder tests in general (and I may be wrong about this) are only looking for minimal dispersion in the vertical axis when doing load development.

I'm sure I'm missing something and thought perhaps you could shed some light on this. I've brought this up in passing on SH before, but nobody has risen to the challenge of explaining it to my dumb ass.

Slow mo high frame rate video shows barrels oscillate in all sorts of directions.

When doing an OCW or Audette ladder test, you not only will see vertical shifts but you will also see horizontal shifts.

The Ladder test prioritizes minimal dispersion and starts with powder charge testing to find minimal vertical dispersion first before moving to seating depth as a follow up test to control horizontal dispersion. POI shifts are not as important as minimal dispersion mainly due to the larger distance the test is usually conducted where wind has a larger effect and POI shifts that can be dealt with afterwards with scope adjustments.

OCW test prioritizes minimal POI shifts and it starts with powder charge to find a range of charge weights that have both minimal vertical and horizontal POI shifts. It can then be followed up with a seating depth test to reduce both vertical and horizontal dispersion. The theory is basically if you have the "optimal charge weight", your POI would not shift and thus not require re-zeroing of a scope, regardless of temperature shifts (especially with temperature sensitive powders; generally low temperature = lower velocity which is equivalent to less powder, high temperature = higher velocity which is equivalent to a higher charge weight), different lots of powder, powder humidity, etc. The charge weight that produces the smallest group does not matter if on either side of the charge weight the POI shifts.

 

[straightshooter1]

Slow mo high frame rate video shows barrels oscillate in all sorts of directions.

When doing an OCW or Audette ladder test, you not only will see vertical shifts but you will also see horizontal shifts.

The Ladder test prioritizes minimal dispersion and starts with powder charge testing to find minimal vertical dispersion first before moving to seating depth as a follow up test to control horizontal dispersion. POI shifts are not as important as minimal dispersion mainly due to the larger distance the test is usually conducted where wind has a larger effect and POI shifts that can be dealt with afterwards with scope adjustments.

OCW test prioritizes minimal POI shifts and it starts with powder charge to find a range of charge weights that have both minimal vertical and horizontal POI shifts. It can then be followed up with a seating depth test to reduce both vertical and horizontal dispersion. The theory is basically if you have the "optimal charge weight", your POI would not shift and thus not require re-zeroing of a scope, regardless of temperature shifts (especially with temperature sensitive powders; generally low temperature = lower velocity which is equivalent to less powder, high temperature = higher velocity which is equivalent to a higher charge weight), different lots of powder, powder humidity, etc. The charge weight that produces the smallest group does not matter if on either side of the charge weight the POI shifts.

Yeah, the barrel's oscillations are complex, yet . . . like in a "complex" sine wave. Minimal dispersion is certainly the goal for all of us. Sometimes I feel like we're all talking about the same thing, only describing it in a different way???

 

[bax]

As I pretty much agree with all that you're saying, ideally we want the bullet to leave when the barrel stops at the anti-node of that wave. But, that would require each shot to have exactly the same velocity . . . and a lot of effort to find the exact timing. So, to be clear, we're trying to get as close to that as possible within a period of that time at the apex of the anti-node (like I indicate with the two arrows). The flatter the wave, the flatter that area . . . which is one of the reasons why heavy long barrels with their lower frequency makes it easier to tune a load than light thin barrels.

View attachment 8050655

No habla on the "anti-node" lingo. I think about it this way - at your "two arrow" spots the barrel points down or up. And for some significant period of time - like the distance between those double-arrows - that direction does not change much. However, move the arrows around to 11 on the x-axis and, during the same time interval, the barrel direction changes a lot. As we increase the powder charge, the muzzle velocity increases and barrel time gets shorter. At the arrow points the barrel direction is more stable for a longer period of time. The range of powder charges that produce that barrel time (and velocity) is wider than it is around 11. According to my made-up theory that explains "nodes". The velocity isn't the same (it makes no sense that it would be the same, the powder charge is different) but the barrel direction IS almost the same - barrel direction change is minimized for those velocities.

Is it true that a heavy barrel has a lower frequency? I would guess (I have zero facts) that the fatter/stiffer/heavier barrel would have a lower amplitude but the same frequency.

 

[bax]

Slow mo high frame rate video shows barrels oscillate in all sorts of directions.

When doing an OCW or Audette ladder test, you not only will see vertical shifts but you will also see horizontal shifts.

The Ladder test prioritizes minimal dispersion and starts with powder charge testing to find minimal vertical dispersion first before moving to seating depth as a follow up test to control horizontal dispersion. POI shifts are not as important as minimal dispersion mainly due to the larger distance the test is usually conducted where wind has a larger effect and POI shifts that can be dealt with afterwards with scope adjustments.

OCW test prioritizes minimal POI shifts and it starts with powder charge to find a range of charge weights that have both minimal vertical and horizontal POI shifts. It can then be followed up with a seating depth test to reduce both vertical and horizontal dispersion. The theory is basically if you have the "optimal charge weight", your POI would not shift and thus not require re-zeroing of a scope, regardless of temperature shifts (especially with temperature sensitive powders; generally low temperature = lower velocity which is equivalent to less powder, high temperature = higher velocity which is equivalent to a higher charge weight), different lots of powder, powder humidity, etc. The charge weight that produces the smallest group does not matter if on either side of the charge weight the POI shifts.

If you shoot ladders with small powder charge changes you can watch the groups get bigger and smaller and wander around on the target. As you said the barrel vibrations are very complex. The barrel is getting longer and shorter - vibrating along its long axis. As the bullet is shoved down the barrel, the rifling imparts a spin on the bullet. But the bullet has mass and force and tries to straighten the rifling inside barrel so the barrel is twisting and untwisting. It is vibrating vertically and horizontally and every possible combination all at the same time.

But I believe that at specific times, the barrel-direction-delta goes to zero. If you adjust your powder charge so that the bullet emerges from the barrel at those times, you get small groups.

Makes me wonder about "hummer" barrels. BR shooters search for barrels that, fed the right load, shoot tiny groups even in less-than-ideal conditions. Maybe bad barrel differ in ways that prevent barrel-direction-delta=zero and "hummers" ring in ways that give longer zero times. Maybe bedding and recoil lugs and stocks matter even more than we thought.

 

[straightshooter1]

No habla on the "anti-node" lingo. I think about it this way - at your "two arrow" spots the barrel points down or up. And for some significant period of time - like the distance between those double-arrows - that direction does not change much. However, move the arrows around to 11 on the x-axis and, during the same time interval, the barrel direction changes a lot. As we increase the powder charge, the muzzle velocity increases and barrel time gets shorter. At the arrow points the barrel direction is more stable for a longer period of time. The range of powder charges that produce that barrel time (and velocity) is wider than it is around 11. According to my made-up theory that explains "nodes". The velocity isn't the same (it makes no sense that it would be the same, the powder charge is different) but the barrel direction IS almost the same - barrel direction change is minimized for those velocities.

Is it true that a heavy barrel has a lower frequency? I would guess (I have zero facts) that the fatter/stiffer/heavier barrel would have a lower amplitude but the same frequency.

It takes more energy to raise the amplitude of a low frequency to the amplitude of a higher frequency. Maybe you can better understand it by thinking in terms of speakers where a woofer require a lot more power than a tweeter???

 

[Rick MandP]

I started reading the thread early. At first I was "ho hum, good stuff but same old stuff". Then people started talking about OCW and I thought (feeling superior), "I'm smart, I know what these guys are talking about". Then some wild man comes in and says that all our children are ugly and I'm pissed! Then I keep reading and I discover that some people try to choose a configuration by looking at velocities on their chronograph and some other people are looking at their targets. I'm confused - what are y'all doing?

I'm in that second bunch. I shoot 3-shot groups where each 3-shot group has the same charge. The loading block has maybe ten rows of cases and there is an increased charge from one row to the next - the delta depends on the case size and powder. I am looking for groups that are round and where three consecutive rows impact in about the same place. I stop when I see pressure. When I find one or two sets like that, I reshoot the same three rows to see if it repeats - mostly they do but not always. If it does repeat, I increase the charge range a little (I want to make sure that I identify the bottom and top end of the sweet spot) and reduce the charge increment to 0.1 grain and reshoot. I now have good gun data from that load and from there I usually pick a charge in the middle of the range and load that. I do not use a chronograph. When I have a load that shoots, I shoot it from 100 out to as far as I can go, writing down the ups. I open Applied Ballistics, configure the cartridge then change the velocity until AB predicts the curve I just measured.

Last weekend, I shot 25 rounds at 1k. When the barrel was new, AB told me that the velocity was 2700 fps and telling me to dial 7.6 for 1k. This has been a good setting for about 200 rounds. But last Sunday I had to dial 7.3 in order for my point of aim to match my point of impact. Apparently something changed and the velocity increased by about 55 fps. I don't KNOW that the velocity changed but that it what it takes to make hits so that is what I use.

It has not occurred to me that I should try to find three different charges that gave about the same velocity. I stopped caring about SD and ES a long time ago - I could never get it to relate to group size so I stopped caring about those numbers. I do care about the average velocity number so I can dial or hold but I don't care what the number is, it is just a parameter in the function that gives me "ups" and windage.

YMMV

This is how I do it. ( no chronograph)...Makes perfect sense and Its still fun , doesnt waste a ton of components and barrel life ,and all i want is a round that hits where Im aiming...I have played around with seating depth but Im pretty far back, .025 -.015

 

[austinflyer]

Interesting discussion. All I know is that I input all of my information into QuickLoad, and the Pmax and Z1 were on top of each other. It indicated that the FPS should be 2524 FPS. I had actually done a ladder a few months back and had highlighted where I thought the nodes were...one was where I was shooting .3 MOA (that's good for me). When I looked at the actual chrono data avg. from that session, it was exactly 2524 fps. So somehow, it matched my real life results without bias, as I didn't even remember what that grouping on the ladder looked like until I went back and looked after running Quickload.