PRS Talk How does being in a “node” actually matter?

[chevy_man]

The simplest answer...


Margin of error.

Nothing is perfect. You'll never get 200 rounds to the exact kernal and even then the powder can vary even in the same can. You'll never seat the bullets perfect, +/- .00005 is smaller than a caliper will measure reliably but it's still not absolute perfect. Brass varies, it's metal and metal isn't perfect. Same goes for the bullets. They may be too close to measure with the average reloaders tools but they're not all absolute perfect.



If you set your load smack in the middle of a node you're giving yourself the best margin of error for every variable to stay inside that sweet spot.


I've shot loads that were great, but .1grn either way the SD's came up from 3 to 25+. I'm not going to depend on that load when I found one at 8 that has 10-12 for .6grn either side.

I've also seen the "scatter node" where I was getting an es of 8 with an SD of 2. But it was 2moa instead of the .5 or less that is normal, all verticle stringing. Powder column and primer were happy there, bullet exit during barrel whip was not. This was on a lighter sporter profile barrel.

 

[Macht]

No offense man, but of course you’re using a formula. A stiffness matrix is a primary component of an Finite Element Analysis. I’ve had to set up and solve loads of these by hand back in my college days. Modulus of elasticity and second moment of area are primary driving factors in your stiffness matrix.

I have to ask, have you ever solved an FEA by hand - no computer ?

To be blunt, I have a M.S. in mechanical engineering. My entire master's project was based on explicit FEA and I've spent the last 3 years of my life developing this barrel dynamics model as my PhD project. I am well aware of the equations behind the curtain, have done simple models by hand and have coded my own 2D solver in MATLAB. I'm not someone who thought they'd just fire up Abaqus in their spare time and fool around. I think this tangent to the main thread has run its course.

 

[Secant]

To be blunt, I have a M.S. in mechanical engineering. My entire master's project was based on explicit FEA and I've spent the last 3 years of my life developing this barrel dynamics model as my PhD project. I am well aware of the equations behind the curtain, have done simple models by hand and have coded my own 2D solver in MATLAB. I'm not someone who thought they'd just fire up Abaqus in their spare time and fool around. I think this tangent to the main thread has run its course.

I wasn't trying to offend you with my last question to you. As an engineer, I’m sure you can appreciate how I thought your below statement was a little strange. As we both know, those software programs are obviously based in formulas, and there are plenty of people that do just start running software programs without a clue to what's going on in the background (just look at how many "why doesn't my ballistic solver work" threads that constantly pop up).

I'm not using a formula, it's a fully 3D finite element model.

As PrecisionUnderground put it, don’t take this as some internet challenge, or me trying to call you out, or any other forum nonsense - I’m trying to hopefully learn something here. As I’m sure you know, modulus of elasticity and second moment of area are essential to understanding deflection and stress in a system. In the context of this discussion, I agree that the relative moduli between steel barrels is likely a small player - however it is a component that needs to be well understood to then evaluate and/or predict the deflections & stresses of any single barrel.

Maybe I misunderstood what you said previously and/or maybe my previous comments were unclear, but I'm very interested in how deflection of an object can be independent from that object's second moment of area. Unless you are saying that "harmonics" is describing something other than barrel 'movement', it's unclear how we would step away from second moment of area or modulus of elasticity to evaluate and/or predict said movement.

If @Dthomas3523 thinks we are too far on a tangent, I can take this to PMs or start a new thread. But in my own mind, these are valid questions and others may find the answers helpful as well.

 

[kindabitey]

Ya'll go be nerds somewhere else

 

[Secant]

Ya'll go be nerds somewhere else

Everybody wants to talk about HARMONICS and pretend they're a reloading scientist until it gets real

 

[Dthomas3523]

Feel free to keep going. It’s a good topic

 

[Precision Underground]

Everybody wants to talk about HARMONICS and pretend they're a reloading scientist until it gets real

Making the sausage.

 

[kindabitey]

It's a great topic, I just have to read it 4 or 5 times to understand it.
It would interesting to see some type of vibration/ harmonic data collected from a match ready rifle, even if it was shot from a bench or prone.

 

[Macht]

Maybe I misunderstood what you said previously and/or maybe my previous comments were unclear, but I'm very interested in how deflection of an object can be independent from that object's second moment of area. Unless you are saying that "harmonics" is describing something other than barrel 'movement', it's unclear how we would step away from second moment of area or modulus of elasticity to evaluate and/or predict said movement.

Guess it looks like people aren't too bored of the discussion yet!

I think I wasn't clear in my one of my previous posts, my experience so far has been that the barrel contour, i.e. the area moment, effects the amplitude of vibration but has a much smaller impact on the frequency. Which would be a possible explanation for why it is supposedly easier to "tune" a load in a heavy barrel than a light sporter, but that the loads often still end up within a grain of one another. I only have access to one contour of test barrel at the moment, but I plan to run a series of lengths and contours in the model within the next couple of months as the basis for a journal paper.

 

[Macht]

It would interesting to see some type of vibration/ harmonic data collected from a match ready rifle, even if it was shot from a bench or prone.

That's kinda what I posted above. Those plots are from an RPR in 6.5 Creed, although it's missing both a scope and the handguard.

 

[Deleted member 10043]

My node is the same for every node. I work up .3 grains until I first see signs of over pressure seated .005 off jammed into lands. I then back off .5 grains. Then I check for seating starting off .005 as before for groups up to .02. The one with the best group is my huckleberry. About every 500 rounds I'll recheck my seating depth. I may have to increase CBTO .003 - .006. Who knows until it is time. You young snappers have developed a very strange sense for the method of least squares.

 

[Dthomas3523]

My node is the same for every node. I work up .3 grains until I first see signs of over pressure seated .005 off jammed into lands. I then back off .5 grains. Then I check for seating starting off .005 as before for groups up to .02. The one with the best group is my huckleberry. About every 500 rounds I'll recheck my seating depth. I may have to increase CBTO .003 - .006. Who knows until it is time. You young snappers have developed a very strange sense for the method of least squares.

This further illustrates my point. This is yet another method that works for you (and others).

I’m sure it works well. If you’re doing things remotely consistent and using good components, that’s the heavy legwork.

 

[Deleted member 10043]

This further illustrates my point. This is yet another method that works for you (and others).

I’m sure it works well. If you’re doing things remotely consistent and using good components, that’s the heavy legwork.

It's all in the squares and doesn't require having to actually calculate or graph anything but it is what most everybody is grasping at . So, if you do graph your MV in increments to solve for the best line yada yada yada...This will blow your mind.

 

[Precision Underground]

It's a great topic, I just have to read it 4 or 5 times to understand it.
It would interesting to see some type of vibration/ harmonic data collected from a match ready rifle, even if it was shot from a bench or prone.

It sounds like we need to define harmonics so we know what to measure. To me harmonics is movement/disturbances *within* the rifle; not movement OF the rifle. That’s how I’ve always looked at it. The only way to measure this would be sensors on the rifle to measure changes in the system in relation to itself, not in relation to space. IMO it’s prob not possible to measure because if the OTB theory is correct you’d never be able to measure 1/10,000 (or whatever it is) of bore disturbance while firing live rounds.

 

[Secant]

Base level description of harmonic motion and natural frequency

 

[Precision Underground]

Base level description of harmonic motion and natural frequency
View attachment 7454729

What are your thoughts on the optimum barrel time paper? That makes the most sense in my head. In a nutshell it says it’s more about disturbances in the bore than actual deflection of the barrel. This lines up with my doubt that a barrel could deflect fast enough for increments of .2gr of powder or .02 seating depth to affect POI the way I know an OCW can. The stress waves he describes as bouncing from bore to action multiple times during dwell time make perfect sense. This is why some say harmonics don’t matter. I think they are measuring the wrong thing.

 

[NamibHunter]

Thats a good question and point.

IMO, you need to be dropping powder as precise as possible. A chargemaster should be able to do it.

And have consistent neck tension across the board. Most are either not measuring or using calipers to measure (which isn’t a good way to measure) their neck tension. I use a pin gauge and spot check.

I think anyone dropping powder close to a kernel and using a mandrel to set consistent neck tension should be able to.

If somebody has the book handy, please correct any misstatemnts below:

Bryan Litz in one of his latest books did an experimental (myth busters) test comparing an expensive powder thrower/powder measure, the RCBS Chargemaster (0.1 grain resolution but closer to 0.15-0.2 grain of actual accuracy), and i think a milligram lab scale (0.02 gn resolution but probably 0.04 actual accuracy due to linearity), and i think a (incredibly expensive) Sartorius lab scale ($2,000) that measures to 0.0001 gram (0.1 milligram, or about 0.002 grain which is about a tenth of a kernel).

From memory, the Chargemaster convincingly outperformed the powder thrower in terms of SD and ES of the loaded ammo, which was kinda expected. The milligram scale (an FX120 equivalent) was only slightly better than the Chargemaster.... and the Sartorius did not give any further improvement.

My read of the chapter was that Chargemaster is good enough for PRS/NRL competitions, and that the FX120 plus autotrickler is maybe probably justified for the BR and F class games, if you are in the top 10. Same very likely applies to the superbly accurate Prometheus setup, around $5,000.

Neck tension: Have also found that you have to run a round object through the neck after sizing, either a mandrel (one that does not grab and bend the brass, with dry lube), or the superb Whidden non-bushing sizing die with a set of differently sized precision ground buttons. Does the job of a mandrel in one step and does not bend the neck, so concentricity remains good. Most dies with sizing buttons work quite poorly, the Whidden if different, as it minimally sizes the neck and does not mangle the neck. Slightly outperformed the Redding Type S in my testing.

BTW: I agree concentricity is not critical unless you compete in BR and you are trying to shoot groups below 0.1”. [Have actually done the test, group size went up 30% (from 0.3 to 0.45”) only when total indicated runout (TIR) exceeded 5-6 thou, which is a lot. Keeping TIR below 3 thou is not that hard.]

Seems to confirm what Dthomas mentioned.

 

[NamibHunter]

BTW: I have done the test several times to find the flat spot in the powder vs speed graph, using 5 shot groups, and yes i found three fairly convincing ‘flat spots’. SD was usually lowest at the flat spots, but group size was not (because positive conpensation was not yet dialed in). That optimization was done subsequently and group size was then pretty good, around 0.3”.

Then made the mistake of repeating the test 3 months later at 20 deg F higher ambient temperature and with 500 more rounds through the barrel... it still had flat spots but they MOVED without my permission! My conclusion was that these flat spots are not as convenient as we may think. They have an expiry date.

Maybe if i did 20 shot groups originally, i would have seen a different picture... maybe the ‘flat spots’ were just slight changes in slope, who knows!

I am convinced that doing less intensive load development work, and shooting more rounds per week will help me improve more. But keeping the OCD under control is harder than you might think.

The loose nut behind the bolt is by far the weakest link, so let’s upgrade that first.

 

[Macht]

What are your thoughts on the optimum barrel time paper? That makes the most sense in my head. In a nutshell it says it’s more about disturbances in the bore than actual deflection of the barrel. This lines up with my doubt that a barrel could deflect fast enough for increments of .2gr of powder or .02 seating depth to affect POI the way I know an OCW can. The stress waves he describes as bouncing from bore to action multiple times during dwell time make perfect sense. This is why some say harmonics don’t matter. I think they are measuring the wrong thing.

First off, I think you need to read that paper again. Chris states that he thinks POI change is driven by the overall barrel movement. Direct quote: "Having said this, I do agree that the POI changes are primarily due to the bending modes, but because they are so low in frequency, they are “smooth” and do not change rapidly over load variations. "

Second, there are parts of his model that seem suspect. He bases the whole theory on the theoretical speed of sound in steel, but if you actually measure a stress wave traveling end to end in a barrel you'll find that it travels about 17% slower than that due to energy going into shear waves. Beyond that, he predicts a nice repeatable pattern of waves with a peak change of about 5 microns in diameter. It's likely closer to a 1/10 of that, and not nearly so neat. Beyond that, the projectile and pressure have their own effects on that muzzle and it ends up looking more like this:

 

[47guy]

BTW: I have done the test several times to find the flat spot in the powder vs speed graph, using 5 shot groups, and yes i found three fairly convincing ‘flat spots’. SD was usually lowest at the flat spots, but group size was not (because positive conpensation was not yet dialed in). That optimization was done subsequently and group size was then pretty good, around 0.3”.

Then made the mistake of repeating the test 3 months later at 20 deg F higher ambient temperature and with 500 more rounds through the barrel... it still had flat spots but they MOVED without my permission! My conclusion was that these flat spots are not as convenient as we may think. They have an expiry date.

Maybe if i did 20 shot groups originally, i would have seen a different picture... maybe the ‘flat spots’ were just slight changes in slope, who knows!

I am convinced that doing less intensive load development work, and shooting more rounds per week will help me improve more. But keeping the OCD under control is harder than you might think.

The loose nut behind the bolt is by far the weakest link, so let’s upgrade that first.

you and i have talked about the OCD part of reloading and funny now that youve been doing all of this testing your coming to realize what i told you...that reloading is the most over thought thing on the planet.

 

[Precision Underground]

First off, I think you need to read that paper again. Chris states that he thinks POI change is driven by the overall barrel movement. Direct quote: "Having said this, I do agree that the POI changes are primarily due to the bending modes, but because they are so low in frequency, they are “smooth” and do not change rapidly over load variations. "

Second, there are parts of his model that seem suspect. He bases the whole theory on the theoretical speed of sound in steel, but if you actually measure a stress wave traveling end to end in a barrel you'll find that it travels about 17% slower than that due to energy going into shear waves. Beyond that, he predicts a nice repeatable pattern of waves with a peak change of about 5 microns in diameter. It's likely closer to a 1/10 of that, and not nearly so neat. Beyond that, the projectile and pressure have their own effects on that muzzle and it ends up looking more like this:
View attachment 7455551

I can’t tell if you’re using semantics to try to prove me wrong or if you don’t understand what is being said. 2 sentences after the quote you posted he says...

“However, since it ruled out the bending modes out as an explanation for the variation in dispersion and velocity deviation, I was still left with no model for these observations.”

What he’s saying is exactly what I said. The large movement of the barrel is too slow to account for the variation we see on target in OCW tests. He calls it “dispersion”. This is what I was referring to.

 

[Deleted member 10043]

Barrel vibrations and harmonics are a secondary reaction and are over emphasized. If you want to see where it is truly minimal you need to plot on a graph each incremental shot than solve for the true line. Data points of shots closest to the true line are where your entire rifle is closest to at rest with minimum disturbances. You may find this is not the MV you are wanting so what are you going to do now if you only have one powder to choose from that is within the acceptable burn rate for that cartridge?

 

[2aBaC̶a̶]

Cant wait to see a conclusion in real world layman's terms.

 

[Secant]

View attachment 7454729

What are your thoughts on the optimum barrel time paper? That makes the most sense in my head. In a nutshell it says it’s more about disturbances in the bore than actual deflection of the barrel. This lines up with my doubt that a barrel could deflect fast enough for increments of .2gr of powder or .02 seating depth to affect POI the way I know an OCW can. The stress waves he describes as bouncing from bore to action multiple times during dwell time make perfect sense. This is why some say harmonics don’t matter. I think they are measuring the wrong thing.

Overall, I think the paper is interesting. I also think it's worth stating that the scientific method is really based around trying to disprove a theory - not looking for ways to prove it. That is usually where I'm at when I'm reading these types of papers or thoughts/suppositions/etc. on the interwebs. So my questioning/thoughts are not based around me trying to be a dick or trying to pretend I'm the smartest dude in the room. With that in mind, here are a few thoughts:

The typical complaint with "observations" that are used by reloaders (the author included), is that two 5-round groups is considered A LOT. Most reloaders are only using 3 data points to draw conclusions, which is nothing statistically, and guys that think they are serious will use 5-rounds. You'll basically never see anybody determining charge weight based on 30, or 40, or 50+ round samples per weight and then setting seating depth with 30, or 40, or 50+ round samples. Let alone going back to adjust seating depth on the "bad loads", and ultimately comparing the bad to the good to see a true difference. I get why guys don't, but it also calls into question the validity of the "good" loads since there really isn't a base line to compare against.

On the other end of the spectrum, the majority of 'scientific' papers that are moved around in the reloading circles seem to be awful light on modeling as well as providing the differentials that back it up (not to mention the observational data that I complained about above). Don't take this as me trying to shit on anyone trying to figure anything out. I just tend to be of the mindset that you need a robust data set in terms of observations, which are back-up by the mechanics, and are consistently and accurately predicted by the modeling program that is being employed if you are looking to truly prove anything. I also get that we can't let perfect be the enemy of great, but I don't think the precision rifle community is at a middle ground yet.


Now specific to the paper, the author's introduction seems to mimic my posts regarding the significant variance in "I", and yet there are 'standardized' loads that are "tuned" for these significantly different geometries. As I've stated multiple times, the variations in "I" are too large to just had wave away and pretend like they don't matter in the context of the "large scale" deflections (think of the slow motion footage from a skinny AK or AR that everyone has seen). And if we say they do matter (which I do say that), then you can't square the circle as to why a 20" M24 contour can have the exact same load (or within 0.2 grains or so) as a 26" #5 or a 24" medium palma, etc. Now admittedly, it's not like I own every length of every contour in every caliber and every chambering - I'm basing much of this off of the input of guys that share their special recipes, which happen to match or be extremely similar to others (and again, this circles back the my complaints regarding observations above).

From the 100,000-ft view and for the purpose of this discussion, it might be worth it to show the standard stress-strain curve. Stress-strain curves are different for different types of materials.

The initial straight line portion (bracketed by 'Hooke's Law" in the image) is the elastic portion and the modulus of elasticity that I keep referencing (aka Youngs Modulus) is described by the rise divided by the run of that initial straight line section. For context Chrome moly 4140 may have a young's modulus of about 205 GPA, 416 SS will be about 200 GPA, copper will be about 117 GPA, and lead is about 13.8 GPA.

While looking at the rate of change of muzzle deformation is interesting, I think we need to put it in context and also look at the actual total changes. As an aside, I think stepping back can be helpful for majority of reloaders or armchair scientists before they try to extrapolate concepts that they read about - especially if they don't have the background to fully understand the concepts. The total deformation associated with a larger contour and/or smaller bore would be less and therefore easier to tune (which is experienced by most), but obviously the heavier and/or smaller calibers are typically far easier to shoot. So what is noise and what is the actual players that matter?

Here are a few questions, and maybe I should think about them a little longer, but off the cuff:

• Looking at total deformation, the difference in contours matters (obviously), and there is still a large variation of contours to contend with. Moreover, we are see many more short(er) barrel rifles today than we were seeing in 10 years ago and definitely 20 years ago. Can we definitely show that the loads for a 26" M24 (for example) cannot work for a 20" or 16" M24?
• The difference in muzzle diameter would correspond to differences in total deformation at the muzzle (seems the Author concentrates on the effects at the muzzle). Can we consistently show that a load developed for a bare muzzle will have different results once the muzzle gets threaded?
• What is the dimensional tolerances of the barrel blanks that we receive, and what is the tolerance in machining that is kicked out by factories and/or smiths (both in reaming the chamber and cutting/crowning the muzzle)? I would be interested to see if/how the stacking tolerances just in the manufacturing process would/could impact load development (I'm not holding my breath for anyone to do this).
• The data set in the paper is small and does not prove or disprove anything from a statistical standpoint.
• Setting aside the small sample size (if that's even possible), the data set provided in the back portion of the paper is quite bad. Look at Figure 5, and then look at Tables 1, 2, & 3. The optimal barrel time for his 27" configuration is 1.240mS. The 1.277mS barrel time in Table 2 was the second best group. The Author does not provide the velocities of each projectile in each group, which would be far more valuable, but the 1.277mS time is right on the edge, and a slight decrease in velocity (increase in barrel time) would be a bad place to be if we go along with the paper as written. Also, look at the group sizes and barrel times in Table 2 and compare to Table 3 - basically no consistency at all.
• For longer barrels, more time would elapse between the points in which the muzzle experienced the stress wave (and associated strain). For shorter barrels, their would be less time elapsing between experiencing the stress wave (and associated strain). So although a short barrel may have more OBTs, there would also have to be a corresponding larger number of "bad" times. Unless I'm thinking of this incorrectly, the shorter barrels would have to be more finicky since a slight variation in barrel time (whether from varying charge weight, seating depth, neck tension, etc.) could result in the bullet exiting during max barrel strain vs min barrel strain. That doesn't seem to match reality for a lot of guys that prefer the shorter barrels.

With all that said, I fully recognize how much time, money, and effort it would take to fully evaluate IF harmonics are having an impact relative to group size, velocity variances, bullet deformation, etc. (from a practical aspect) and then determining to what degree. A single barrel in a single caliber at a set length isn't going to be enough. I think it's great whenever anyone takes any amount of time to try and evaluate this kind of stuff. I also think it's appropriate to be skeptical.

Overall, I think the issue is being solved much faster on the manufacturing side compared to the understanding that is coming out of the scientific side. Not to mention, generally precision rifle shooters are better fundamentally and more informed now more than ever. As I said before, if we assume that harmonics are a significant player, it is still only relative to the variances in the load that is being developed. I think this dovetails directly into what the OP has stated/questioned.

Sorry for the long winded reply, but you literally asked for it, haha.

 

[NamibHunter]

Cant wait to see a conclusion in real world layman's terms.

Not saying Mark or Bryan Litz are the ultimate authorities, but they both have done some amazing things over the years.

This is the Mark and Sam video on Utube. Look at minute 6:00 onwards:



He is hitting a 24” steel target out to 5000 yards plus. That is a half MOA target at that remarkable distance and the bullet is of course well into the subsonic range, with the bullet coming in at a steep 20-30 degree angle. He is not using ladder tests or trying to exploit nodes, he load as fast as max pressure will allow. Spends time making sure the rifle recoils perfectly every time, using a video camera.

This is the Litz video, from minute 1:30 onwards:



Philosophical argument that a half minute load is good enough for ELR and that practice time is more valuable than spending a lot of time in the roading room and testing different loads.

 

[Deleted member 10043]

Cant wait to see a conclusion in real world layman's terms.

PRS Talk - How does being in a “node” actually matter?

The simplest answer... Margin of error. Nothing is perfect. You'll never get 200 rounds to the exact kernal and even then the powder can vary even in the same can. You'll never seat the bullets perfect, +/- .00005 is smaller than a caliper will measure reliably but it's still not absolute...

www.snipershide.com

 

[Dthomas3523]

Cant wait to see a conclusion in real world layman's terms.

Load what you want. Make sure it has consistent acceptable ES. Make sure the groups are acceptable for you.

Make sure you have a working BC or custom curve that works with the speed your chrono gives. Chrono when you go somewhere with substantial change.

That’s the applied solution.

 

[Deleted member 10043]

Load what you want. Make sure it has consistent acceptable ES. Make sure the groups are acceptable for you.

Make sure you have a working BC or custom curve that works with the speed your chrono gives. Chrono when you go somewhere with substantial change.

That’s the applied solution.

Perfect!

 

[Macht]

I can’t tell if you’re using semantics to try to prove me wrong or if you don’t understand what is being said. 2 sentences after the quote you posted he says...

“However, since it ruled out the bending modes out as an explanation for the variation in dispersion and velocity deviation, I was still left with no model for these observations.”

What he’s saying is exactly what I said. The large movement of the barrel is too slow to account for the variation we see on target in OCW tests. He calls it “dispersion”. This is what I was referring to.

I think you're the one not understanding the terminology. POI change (what an OCW test is based on) is the location of the center of the group. Chris contends that this is due primarily to bending nodes. Dispersion is the size of each group, and Chris spends the bulk of the paper theorizing on what could cause said dispersion. Summed up, his paper states: POI = bending, dispersion = radial stress waves.

 

[NamibHunter]

Cant wait to see a conclusion in real world layman's terms.

How about this:

1) Pick your caliber and bullet based on intended use. For example you might select 6 mm CM or 6 BRA for PRS competition and maybe you will pick the 110 gn Hornady A-tip. Or select 375 Cheytac Improved for ELR and perhaps pick the 400 gn Cutting Edge projectile. Buy a single batch of 1000 bullets.

2) Buy or build a rifle for that particular bullet, get a reamer made up, and cut the freebore for the selected projectile, and get the required twist rate in a heavy barrel.

3) Acquire good reloading gear like a ChargeMaster or possibly a milligram scale like an FX120. Get a Labradar and take it with you everywhere the rifle goes. Use custom drag curves in your ballistic solver.

4) Ignore the barrel nodes, just find max pressure, back off 0.5 gn, and develop one load via seating depth optimization that shoots 5 shot groups at or below 0.5 MOA at distance on low wind days, exploiting positive compensation. If SD is below 10, just be happy and go shoot. Control your OCD and avoid trying to develop a 0.25” load, or a load with a 4 fps SD. You will just wear out your barrel. And it will eat into your training time. I know - because this used to be ME!

5) Load a 1,000 rounds as best you can, and shoot that until it is all gone. Avoid visiting the reloading room, control your OCD urges, don’t chase the lands, and rather go practice every time there is a strong wind.

6) Order two spare barrels 3 months ahead of time. Take your wife out every Friday evening, so you can remain married.

 

[Snuby642]

That's the second prs shooter that has explained it the same way.

What dt said

 

[Dthomas3523]

How about this:

1) Pick your caliber and bullet based on intended use. For example you might select 6 mm CM or 6 BRA for PRS competition and maybe you will pick the 110 gn Hornady A-tip. Or select 375 Cheytac Improved for ELR and perhaps pick the 400 gn Cutting Edge projectile. Buy a single batch of 1000 bullets.

2) Buy or build a rifle for that particular bullet, get a reamer made up, and cut the freebore for the selected projectile, and get the required twist rate in a heavy barrel.

3) Acquire good reloading gear like a ChargeMaster or possibly a milligram scale like an FX120. Get a Labradar and take it with you everywhere the rifle goes. Use custom drag curves in your ballistic solver.

4) Ignore the barrel nodes, just find max pressure, back off 0.5 gn, and develop one load via seating depth optimization that shoots 5 shot groups at or below 0.5 MOA at distance on low wind days, exploiting positive compensation. If SD is below 10, just be happy and go shoot. Control your OCD and avoid trying to develop a 0.25” load, or a load with a 4 fps SD. You will just wear out your barrel. And it will eat into tour training time. I know because this used to be ME!

5) Load a 1,000 rounds as best you can, and shoot that until it is all gone. Avoid visiting the reloading room, control your OCD urges, don’t chase the lands, and rather go practice every time there is a strong wind.

6) Order two spare barrels 3 months ahead of time. Take your wife out every Friday evening, so you can remain married.

Don’t worry with positive compensation for multi distance/prs stuff

 

[Jackomason]

shooter B has the advantage. he can blame his miss on his load while shooter A has to accept that he just sucks....

 

[NamibHunter]

In the spirit of full disclosure, i should mention that the total budget for steps 1-6 could run anywhere between $5K for a 6BRA rifle using budget components, or $9K for an ELR rig using premium components.

Assuming you already own the $3K scope and have previously spent $2.5K for a Charlie Tarac. There are budget reasons why most of us reload the same batch of 100 cases... and avoid the super consistent $1.50 monolithic bullets. And why we have been thinking about competing in ELR, and have yet to take the plunge.

 

[Dthomas3523]

I define node as a velocity flat spot. And I don't always get one. My last two Dashers using Varget had an even 10fps per .1gr increase. Switching to 4350, I did get a flat spot at 34.7 - 35.2gr/ 2900fps. Yes, you can absolutely shoot great groups and perform well in PRS without a node. And I'm fine with that for certain guns. TBH, Im not super thrilled about 1/2 moa groups. My personal standard is 1" at 300yds. Even if its overkill for PRS or other action precision rifle shooting sports. I like to keep the precision in precision rifle.

Yes, you can buy all the best in expensive reloading tools...IDODs, Prometheus, Zero press and shoot nothing but Varget in BR cartridges....just to pump out minimally thrown together 1/2" loads? Totally backwards to me. My goal is pump out 1/4 to 3/8" ammo in progressive presses. I am currently working on 6GT using StaBall in a 650. Getting the bullet feeder to consistently drop 6mm bullets is a bitch. Thrown powder. Full progressive. Ive got a 6BR toolhead throwing 8208. And a 308W toolhead throwing BL-C2, shooting on or about 1" groups at 300yds and single digit SDs.

I've never historically specifically loaded looking for a flat spot in velocity. But if I found one I would exploit it. Then a colleague wanted a 6.5 Creed. I helped him find a Tikka CTR 24" 6.5 Creed. Put it into a KRG Bravo. I helped him buy 1000rds worth of components and did load development for him. I found the biggest flat spot I've ever seen from 43 gr to 44.5gr of StaBall in his rifle. Bulk 140 ELDs from Midsouth. Virgin Hornady 6.5 Creed brass. CCI 200 primers. All loaded on a 650. Factory 24" Tikka barrel. At first I was trickling using an FX 120 to load ladder tests. After finding a flat spot. I picked middle of the node and loaded rounds throwing and rounds trickling to compare. This load would shoot a misshapen hole at 100 and 1" at 300. The trickled load shot 4 fps SDs and the thrown load shot 2.3fps. StaBall threw well but not 2.3fps well. The over and under-throw white noise hid in the wide flat spot. Then I loaded 1000rds in one go for him. He's still shooting it and texted me two weeks ago telling me how accurate it was.

I've repeated that with 308 and am working on 6GT. I wasn't able to do it with 6BR. I suspect 8208 just isn't going to give it in between 2830 and 2900.

I'm trying to leverage flat spot nodes to pump out accurate ammo very quickly using less than precision equipment and more thought out load development. Faster loading, more accurate, at the cost of more range time doing load development. I think there's a cool-guy attitude about how a guy figures out what matters and what doesn't and guys like to talk like load development is for fudds. Sure, spends thousands of dollars on BR loading equipment just to half ass load development....bc spending time shooting rifles...sucks?

I just stay away from talking about velocity flat spots because people argue too much about them.

But when you ask a naysayer if they tried different powder/primer combinations, they usually say no. Or you find out their loading process isn’t refined enough for them to have any valid data to make an informed decision.

For some reason, PRS types will never try different powders/primers (which is fine as it’s prs). But then they decide they have data to make an informed opinion on velocity flat spots not existing. So, it’s talking out of both sides of their mouths. Which is why I just avoid the conversation.

And I completely agree with making the best ammo you possibly can. And I typically do a lot more testing and development than one would believe from reading the initial posts. Though it is not necessary for practical shooting.

What I’m mainly pointing out is that many shooters either don’t know what really matters or are chasing something they either don’t need or it’s the wrong time in their progress as a shooter to be messing with a subject or skill.

I’m also attempting to drive home the point that most shooters are looking at the wrong thing when something goes wrong. In this case the subject is ammo. Guys will develop a load that shoots fine. But they take it to distance and either they mess up as a shooter, or the bullets don’t perform consistently. Then they go start tweaking powder and such when it’s a shooter or bullet issue.

Too many myths and such exist from years ago and many (possibly most) shooters don’t understand things such as ammo in a broken down and piece by piece way in which accurately diagnose what’s really going on.

 

[Dthomas3523]

Not to mention, there are different kinds of flat spots.

The obvious example would be:

Avg velocity:

2700
2725
2730
2735
2760

This is the common understanding of a flat spot.

But, let’s look at an overlooked type

2700 (ES 40)
2720 (ES 20)
2740 (ES 18)
2760 (ES 21)
2780 (ES 42)
2800 (ES 38)

While the average velocity kept increasing per powder charge, the very low ES at 2720-2760 is another version of a flat spot. If you’re running 2740, the low ES keeps everything as close as possible velocity wise should something have changed.

Now the question would be, are you shooting a discipline where something can suddenly change enough to be detrimental to the shooter. In PRS, likely not the target size will handle the error. Something like F class.....not so much.

So, while I will perform load development, I do so casually. Meaning if I don’t have time, I can use most anything and be fine. But if I do have time, I’ll do the development.

Or I’ll do development over the course of several practice trips. I’ll shoot a standard load, but take a few of other things and test.

For example I’ll run my dasher with 30.0 varget and .020 off lands. I’ll take some powder charges to practice session and run on chrono. Next session the same 30.0, and I’ll take the chosen powder charge and run seating depth.

So, now I may have 400 rnds on my dasher barrel from practice and matches with 30.0 and .020, but I also found that 30.8 and .038 off lands is what I’ll use for the next 1600 rounds.

 

[samb300]

I have been very loosely keeping up with this thread as the posts have gone up, but the velocity flat spot talk brings me back to one of my initial questions. Is a velocity "flat spot" powder charge dependent, or velocity dependent?

Meaning, as your barrel wears and slows down, or the temperature outside is significantly colder, are you still in that "flat spot" even if you are 50fps slower, but using the same powder charge? Or should you add powder until you get back to the same velocity?

My 6GT has slowed down a lot in from 200 to 800 rounds. Not sure why. But even though the load I've been using is producing 70fps less velocity, it is still shooting small groups with a low SD/ES. Should I add a bunch more powder to get my speed back up? Waste time and money on doing another ladder test? Leave it alone?

I shot it as-is and it was great, I didn't have the time (and am too lazy) to run another ladder before a match weekend.

 

[samb300]

Im guessing you haven't chased the lands. Velocity will decrease as you seat the bullet farther away from the lands, ....or as the lands recede from the bullet. You can probably either add more powder or chase the lands.

I did not. 70fps for 0.045” of throat erosion seems a bit extreme.

Edited to add: this doesn’t address my question, either, regarding the “flat spot” being powder dependent or velocity dependent.

 

[NamibHunter]

Good discussion on what makes a node pack up and move elsewhere.

Have read posts over the years that claimed that a good rifle that has a nice wide flat spot (and low ES) shooting 140s between say 2740 and 2765 fps will also have a flat spot in the same speed range when shooting 120s. That has not been my experience, even when using the same powder. Curious what you guys have seen?

Agree that load development is a very useful tool in the reloader’s toolbox. Depending on the task at hand, it may be optional or it may be absolutely required. For the new shooter, it is probably something that can wait for later. Start with good factory ammo like Berger, defer the purchase of all that expensive reloading equipment to later, and rather use that money to attend a training course to learn good fundamentals, practice for 3 or 4 months at shorter distances where wind and vertical stringing are not the dominant factors, get down to 0.5” or better groups at 100, then move to 400 and beyond. Now this (moderately experienced) shooter will probably find that a low SD helps quite a bit and reloading is a benefit if he wants to hit the 3” plate at 600 with good regularity, and he will have to learn how to do wind reading. Time to acquire some gear, and the RCBS 1500 might well be good enough. One more step in his journey to competitive shooting. Once he thinks he is ready to shoot his first 2” group at 600, it will be a good time to get into careful load development including positive compensation. And at about this time he is replacing his original factory barrel with a Bartlein.

Just my two cents.

 

[Gilly]

We all could have found many nodes whether they really exist or not in the time it took to read let alone author this thread. If you’re a good enough shooter you don’t need to find the smallest shooting lowest ES load by tuning it and would rather take random load and get numbers and go shoot that’s great. Some of us like me need all the help we can get and will go OCD and fine tune a .25 but it’s on my time and components not yours!

Call it a node or not, and whatever method you want but I can most likely find a combination in 25 rounds or less that is 20-30% more accurate and 20-30% lower ES than the random acceptable .5”/10 SD range you suggest we settle on. Tuning a load gives the shooter more margin of error to have a load tuned as such. If I can tune a load to shoot .25 instead of .5 that gets me an extra .25 of wind budget (2.5” at 1000 yards) or wobble (1” at 400 yards) to pick up an extra point when my wind call is off or shooting off an unstable position. It’s the difference between edge of plate or off the plate in some cases.

 

[Dthomas3523]

We all could have found many nodes whether they really exist or not in the time it took to read let alone author this thread. If you’re a good enough shooter you don’t need to find the smallest shooting lowest ES load by tuning it and would rather take random load and get numbers and go shoot that’s great. Some of us like me need all the help we can get and will go OCD and fine tune a .25 but it’s on my time and components not yours!

Call it a node or not, and whatever method you want but I can most likely find a combination in 25 rounds or less that is 20-30% more accurate and 20-30% lower ES than the random acceptable .5”/10 SD range you suggest we settle on. Tuning a load gives the shooter more margin of error to have a load tuned as such. If I can tune a load to shoot .25 instead of .5 that gets me an extra .25 of wind budget (2.5” at 1000 yards) or wobble (1” at 400 yards) to pick up an extra point when my wind call is off or shooting off an unstable position. It’s the difference between edge of plate or off the plate in some cases.

I promise your SD is rarely much lower than 10 if you take a large enough sample. And it’s almost never going to be close to 5 or less.

I also promise that most shooters aren’t capable of long term .5moa shooting. The groups everyone posts will move from 2 o’clock today and be at 6 o’clock tomorrow.

What you think you’re accomplishing, you’re likely not. Most just either don’t shoot enough or aren’t honest enough with themselves to realize.

I see the .25 vs the .5 argument all the time. And I’ve rarely seen a shooter that could shoot the difference under realistic conditions or even have the ammo they believe they have that is actually capable.

This thread is just as much about lying to ourselves as it is about what matters more.

 

[Dthomas3523]

Not to mention most of the “tuning” people think they are doing isn’t really doing much.

If people tested long term, they’d find out a lot of what they “tuned” doesn’t stay in tune.

 

[Gilly]

I promise your SD is rarely much lower than 10 if you take a large enough sample. And it’s almost never going to be close to 5 or less.

I also promise that most shooters aren’t capable of long term .5moa shooting. The groups everyone posts will move from 2 o’clock today and be at 6 o’clock tomorrow.

What you think you’re accomplishing, you’re likely not. Most just either don’t shoot enough or aren’t honest enough with themselves to realize.

I see the .25 vs the .5 argument all the time. And I’ve rarely seen a shooter that could shoot the difference under realistic conditions or even have the ammo they believe they have that is actually capable.

This thread is just as much about lying to ourselves as it is about what matters more.

I don’t buy the “most people can’t shoot the difference” excuse. For any given trigger pull regardless of setting having a .25 moa system will put more rounds POI closer to POA than a half moa system will, its science. So I don’t care if you have half moa wobble or 1.5 wobble it’s still an advantage to have a better load!

Call it compensation for poor fundamentals but I feel at a disadvantage to shoot a match with a .5-.75 rifle compared to one that I know can shoot under 1.5” at 500 yards. The last match I shot my dasher just back from a new barrel wouldn’t shoot anything under .6-.7 no matter what I did. I took it to the match anyway and can say I noticed a difference compared to what it had been running the previous barrel. It has since gone back to the gunsmith who confirmed he couldn’t get it to shoot any better and found an issue that was no fault of his or mine and now it’s back in the .2’s.

 

[JustSendit]

I promise your SD is rarely much lower than 10 if you take a large enough sample. And it’s almost never going to be close to 5 or less.

I also promise that most shooters aren’t capable of long term .5moa shooting. The groups everyone posts will move from 2 o’clock today and be at 6 o’clock tomorrow.

What you think you’re accomplishing, you’re likely not. Most just either don’t shoot enough or aren’t honest enough with themselves to realize.

I see the .25 vs the .5 argument all the time. And I’ve rarely seen a shooter that could shoot the difference under realistic conditions or even have the ammo they believe they have that is actually capable.

This thread is just as much about lying to ourselves as it is about what matters more.

This is really nail on the head, long range shooters are the worst at small sample size conclusions!

A couple of weekends ago I tested your approach you outlined, brand new 6cm barrel, I dropped 40.8gr (low end of VV recommendation) of n555 behind a 109berger that was .030 off. SD 9 over 30 rounds, ~.5moa, I did very well winning a club match. Any misses were not due to group size or ES.

I did no load development I dropped powder with an A&D, used quality dies and made good measurements.

I think having solid DOPE out to distance, that has been trued and confirmed under multiple range days supersedes hours chasing very low SDs and .25moa, for most applications. I know it’s entirely possible to have both but I think the later is more piece of mind and confidence building than required.

 

[Dthomas3523]

I don’t buy the “most people can’t shoot the difference” excuse. For any given trigger pull regardless of setting having a .25 moa system will put more rounds POI closer to POA than a half moa system will, its science. So I don’t care if you have half moa wobble or 1.5 wobble it’s still an advantage to have a better load!

Call it compensation for poor fundamentals but I feel at a disadvantage to shoot a match with a .5-.75 rifle compared to one that I know can shoot under 1.5” at 500 yards. The last match I shot my dasher just back from a new barrel wouldn’t shoot anything under .6-.7 no matter what I did. I took it to the match anyway and can say I noticed a difference compared to what it had been running the previous barrel. It has since gone back to the gunsmith who confirmed he couldn’t get it to shoot any better and found an issue that was no fault of his or mine and now it’s back in the .2’s.

You don’t have to buy it for it to be true. Take a log book and start gathering data over thousands of rounds.

The minute you say “I feel” and not “here is what I can show”, you’re speaking anecdotally and that’s no longer a logical debate. Just an emotional one.

Obviously confidence in your equipment is important. But if you “feel” at a disadvantage with a .7 rifle......you have more important things to work on that turning it into a .25 rifle.

 

[Dthomas3523]

How much "tuning" do you think people do?

You said tuning for a load isn't necessary but acknowledged that it could ...do something. You kind of make it sound like you don't tune at all. But at least enough to reach a target MV. And then seating depth for accuracy. But then other folks have jumped on this thread and referenced their "tuning" (whatever that is). And then you replied, I bet if you tested long term your "tuning" isn't actually doing anything. And then you said, I bet you're "tuning" also doesn't stay in "tune". You've also mentioned that you probably do more load development (tuning?)than it would appear, or something to that context.

At this point I'm confused. What are we defining as an adequate amount of "tuning"? What is a superfluous amount of "tuning"? Who decides who's "tuning" is a sham?

You’re just twisting words at this point.

I stated that most “tuning” people do isn’t what they think. Meaning most people haven’t shot enough or experimented enough to know what they really are and aren’t doing.

For example, the people who claim their load that had good chrono numbers and held their accepted group size at 100......claim the load “fell apart at distance” and then go tinkering with powder charge. They have absolutely no idea what really just happened.

That’s just one example. There are many more.

To sum it up simply, most shooters don’t shoot even close to the amount of rounds they would have everyone believe or enough to have any real data. And most shooters regardless of round count, have no idea why they do what they do. They just do what they have seen passed down over the years or heard about.

 

[Dthomas3523]

This is really nail on the head, long range shooters are the worst at small sample size conclusions!

A couple of weekends ago I tested your approach you outlined, brand new 6cm barrel, I dropped 40.8gr (low end of VV recommendation) of n555 behind a 109berger that was .030 off. SD 9 over 30 rounds, ~.5moa, I did very well winning a club match. Any misses were not due to group size or ES.

I did no load development I dropped powder with an A&D, used quality dies and made good measurements.

I think having solid DOPE out to distance, that has been trued and confirmed under multiple range days supersedes hours chasing very low SDs and .25moa, for most applications. I know it’s entirely possible to have both but I think the later is more piece of mind and confidence building than required.

Good stuff.

This is where the “most shooters don’t shoot enough or test enough to have a good grasp on things” comes in.

If your velocity is consistent, you have a good consistent BC or curve (verified through multiple range trips as you said), and acceptable group size, there’s literally nothing else to the equation. It’s very simple in theory.

“Nodes” in the past made up for the cumulative error from the smaller errors in powder sensitivity, charge weight variance, bullet to bullet inconsistencies, optical chrono or no chrono, etc etc etc.

We have progressed enough in all these areas that our cumulative error is much, much smaller.

Add in the fact that we can now take a chrono (or someone will have one) wherever we go and fill in the missing piece of info we didn’t have when traveling prior to all this. Now you have all the answers again for your location.

 

[JustSendit]

What happened to the GT?

I won a free barrel and chamber job, unfortunately the smith didn’t have GT on hand so I went with 6cm.

 

[Dthomas3523]

Like I’ve said since the beginning, everyone has either seen or experienced every reason for a bad or incomplete match. Burned out barrels, loose screws/bolts/brakes, scope goes down, carbon ring, mag feed failures, didn’t dope the rifle correctly etc, etc, etc.

I have never experienced, heard, or seen (and no one in the thread has been able to relay experiencing, hearing, seeing) an issue that was due to poor load development or falling out of a node.

So, that leads to a couple possible conclusions:

1: everyone is doing load development properly

2: it doesn’t matter as much as people think


Pretty sure option 1 is all but impossible.

 

[Raufoss]

I believe this is what Bryan/Amil we’re talking about in one of the no bs BC podcasts with Frank, he was saying he never bothers looking for a node, he finds the velocity and es/sd numbers he wants and then goes from there. Said it was more important for every charge to be thrown perfect to the kernel than to be in a node.

well that resume being in a node.... getting the ES/SD you want is being in a node.

Try shooting the Ko2m with a random load doing jack shit.

In the OP scenario shooter B gets the velocity he wants and just assume his number are good. It’s fine when you vanilla it...

In reality you’ve loaded to a specific speed and your getting decent SD’s your in a node.

Groups mean shit and are tuneable with the jump.

Otherwise it’s pretty simple you end up in a scatter node and you will know it instantly..

No debates to be have here...