Velocities decrease with higher charge sometimes...why?

[parkerg31]

Why do speeds seem to drop sometime with a higher charge? I have wondered this for a while but have always attributed it to me being a inexpireicned reloader using not the best equipment so it was my fault. But, this ladder today was done with 147 gr ELD-M and H4350 and I took the upmost care in making sure that I did everything correct. I have all new reloading equipment that is not hornady anymore and I am experienced enough now to at least eliminate rookie mistakes. I made sure to take all human error out of this test, yet still the velocities sometimes drop with a higher charge. Can anyone drop some knowledge bombs as to why this is? Below is the chart for the shots.

Side note. Rifle is a RPR with a stock barrel. I have a load with the 140s that shoot one hole groups with a 2.3 S.D so I don't attribute this to the rifle.

 

[pmclaine]

My theory.....where you have your accuracy nodes you will find things kind of flat line.

Id expect still a rise in velocity just maybe not as much that occurs where rounds are scattered.

Now the node also has to play with the frequency of the barrel and where it exits the bore in the whip timing.

So I dont know the physics of it but did it look like at those two points your POI was flat/consistent?

Thank you for posting so I could posit on this drawing assumptions out of my ass.


Edit Add------If you see a stock chart doing that buy when its at its drop from the high

 

[Milo 2.5]

If that is one shot per charge, I'd disregard it.

 

[parkerg31]

If that is one shot per charge, I'd disregard it.

Disregard the whole ladder or the slight drop of speed?

 

[pmclaine]

Interesting it appears to occur at regular intervals.

My instinct is there is some sort of actual science occuring.

 

[Chalkeye]

What chrony?

 

[parkerg31]

What chrony?

Magneto speed. Its consistent and runs without issue. Checked on known velocity round before test

 

[Milo 2.5]

Disregard the whole ladder or the slight drop of speed?

The speed drop, not sure what your ladder looks like, I only see a graph of speeds.

 

[47guy]

If that is one shot per charge, I'd disregard it.

this right here^^^....its a ladder test...you have a decent node at 40.3 to 40.7 and another at 42.1-42.3...id shoot 42.5 just to see if it stayed in that flat spot and go from there.
as far as causes...could be several things...neck tension and or case capacity are the first two that come to mind....variances in seating depth if your close to the lands.
is this virgin brass you shot this ladder test with?

 

[parkerg31]

this right here^^^....its a ladder test...you have a decent node at 40.3 to 40.7 and another at 42.1-42.3...id shoot 42.5 just to see if it stayed in that flat spot and go from there.
as far as causes...could be several things...neck tension and or case capacity are the first two that come to mind....variances in seating depth if your close to the lands.
is this virgin brass you shot this ladder test with?

It is once fired Nosler brass. Full length sized. All the rounds were the same seating depth and it isn't that close to the lands. They're loaded to 2.850"

 

[spife7980]

Disregard the whole ladder or the slight drop of speed?

That’s not a ladder, it’s a velocity graph. And the low spot is a fluke, shoot three more of that charge weight and I bet the average falls in line.

 

[47guy]

then its just like shooting 5 or 10 over the chrony to check your ESs and SDs...some are higher some are lower...ive only had a couple of times where ESs where 0 or 1fps difference...several in the 2s and 3s but most times when i shoot more than 5 or 10 over the chrony i end up in the mid teens to low 20s

 

[oldnmkid]

Maybe you need a hotter primer as you increase the powder load. Just guessing, don't know.

 

[stello1001]

Are these all single shots or 3/5 shot average speed per powder charge???

 

[918v]

I think there are at least two different kinds of barrel harmonics. One is a whipping action due to recoil which can be mitigated by increasing barrel rigidity. The other, theoretically, is swelling~constriction of the bore caused by the shock wave of combustion. The trick, I think, is to get the bullet to ride the bore constriction to seal off as much of the combusting gasses as possible behind the bullet.

Adjusting the oal should take care of it.

 

[mdmp5]

The trend is up, but yes you will see velocity drops along the way. I actually read a paper on this not too long ago. The discussion just said that increased charge does not automatically correlate with increased velocity every time.

 

[Deleted member 10043]

It has already been explained by a couple of people in layman terms. People, read the entire thread. OP stated he eliminated all rookie mistakes except he forgot about lack of spread for a single load when he is loading at .2 intervals. Don't do this shit without a rudimentary knowledge of regression and using your chronograph as a statistical tool properly. That is exactly why the output of the chronograph has statistical results. Also, .2 intervals is going to cause immaterial differences in your results. I generally, reload at +/- .1 and get single digit SD and acceptable spread in the high teens or greater. Thus, loading at .2 intervals is going to show intermingling and immaterial results from one load to the next. Nodes and harmonics only exist because people don't know basic statistics. It is probably the biggest area where experienced shooters don't know shit and just made up these two terms to make up for it based entirely on trial and error in search of a falsely perceived phenomenon.

This, will give you an idea though not entirely on topic but definitely in the ballpark. We don't want to leave the OP in the dark with short and sporty answers that don't really teach anything.

https://www.24hourcampfire.com/chronograph.html

 

[powerspc]

I don’t know enough about the ballistics or the physics but I know fair amount about graphing data and in my opinion there’s not enough; data that is. Is this data repeatable, i.e., if you loaded the same charges, same powder, same primer, same brass and shot in the same conditions (temperature, humidity, etc.) would this data repeat? My guess (and it’s only a guess) is probably not. The overall trend is up which is what you would expect, yes there are a few anomalies but I would describe them as just that, anomalies.

 

[Deleted member 10043]

I don’t know enough about the ballistics or the physics but I know fair amount about graphing data and in my opinion there’s not enough; data that is. Is this data repeatable, i.e., if you loaded the same charges, same powder, same primer, same brass and shot in the same conditions (temperature, humidity, etc.) would this data repeat? My guess (and it’s only a guess) is probably not. The overall trend is up which is what you would expect, yes there are a few anomalies but I would describe them as just that, anomalies.

This is a good example on why people should read the entire thread to avoid posting the same useless information Pete and Repeat already posted

 

[Milo 2.5]

This is a good example on why people should read the entire thread to avoid posting the same useless information Pete and Repeat already posted

WTF? I can sleep now knowing you are on it. When an op starts with "I shot this ladder today" and then posts a pic of a speed graph instead of a target, what do you expect to happen?
Then goes on to say he has a one hole load with sd of 2.3, he's going to have to work harder than this to duplicate that load. It was never explained just what the end game was shooting the .2gr charges either, and then wont answer if it was one shot, or 2, or 3, blah blah

 

[Deleted member 10043]

You assumed incorrectly I was referring to you. But since you bring yourself up why didn't you post something righteous and hopeful for a change? Plus, it is just a saying. How was I to know your name is really Pete.

 

[canezach]

I've had this happen a few times., and I was using 3 to 5 rounds at each charge weight. I would see a pretty linear increase in velocity, which corresponds to the increased charge weight, but then I'd have a charge weight where the velocity was slightly lower than the preceding weight. For example, 40 grains was 2700 fps, 40.3 gave me 2720, 40.6 was 2750, but 40.9 was 2745. If I took the individual velocities from 40.6 and 40.9, they would all be within 10 to 15 fps. I will agree with the others that said if it's just one round, ignore it, load a few more of those charge weights, and repeat.

 

[Milo 2.5]

You assumed incorrectly I was referring to you. But since you bring yourself up why didn't you post something righteous and hopeful for a change? Plus, it is just a saying. How was I to know your name is really Pete.

Truthfully, I do not know how to respond correctly, like I said, not certain what the goal is.

 

[Milo 2.5]

It has already been explained by a couple of people in layman terms. People, read the entire thread. OP stated he eliminated all rookie mistakes except he forgot about lack of spread for a single load when he is loading at .2 intervals. Don't do this shit without a rudimentary knowledge of regression and using your chronograph as a statistical tool properly. That is exactly why the output of the chronograph has statistical results. Also, .2 intervals is going to cause immaterial differences in your results. I generally, reload at +/- .1 and get single digit SD and acceptable spread in the high teens or greater. Thus, loading at .2 intervals is going to show intermingling and immaterial results from one load to the next. Nodes and harmonics only exist because people don't know basic statistics. It is probably the biggest area where experienced shooters don't know shit and just made up these two terms to make up for it based entirely on trial and error in search of a falsely perceived phenomenon.

This, will give you an idea though not entirely on topic but definitely in the ballpark. We don't want to leave the OP in the dark with short and sporty answers that don't really teach anything.

https://www.24hourcampfire.com/chronograph.html

I guess I may have been hard on you in a post, I too do not like the term node, it's misconstrued and used too much and out of context. But I do think they exist, in the form of optimal barrel times, But I admit, even though I may believe in the theory, not sure how it is measured accurately. We have software, and we can manipulate it, but still we go off downrange results.
I think a guy can use a chrono to do initial load development, but never use it as a standard. I've seen tight numbers produce extremely accurate results, but I've witnessed the opposite too. I myself use a magneto from start to almost finish, and have used a chrono this way for years.
I have a lot of LR rifles built for myself, this yr alone I'm at 4, the average cost of basic components is 38-4200 per. I demand accuracy, not benchrest accuracy, but repeatable accuracy. I do not chronicle my works, but this Dasher for my Godson needed a story line.
I started with hydro formed brass and CFE 223, it was solid. After fired, it lacked, I went to H 4895, 105 hybrid, first pic is 4 at 500 yards, I did not dare shoot the 5th, two hits apiece on top of each other, not much vertical dispersion.
.
So while shooting, at 1K did not like the results. One morning I hit the range at 5:30, knowing full well going in the load needed something. I was shooting into the sun and not easy to spot hits on white plate, Kahles 6-24i, smkr. The left hit was me getting on plate, the berm on the hanger was wet and not coughing up splash, then 2 on bottom of the plate, centered up, 3rd was high left, I went with sight picture, fired # 4, from my vantage it went in with the 2 lower, but was even higher.

Well, I had done some neck work to the brass on 2nd firing, going down to a .266" bushing, I knew downrange it was not optimal, so I did a .265 partial for even more tension, here s 3 shots, the red dot my aim point 1.5", as I said it was tough to see the target with the sun directly behind the target. I fired this group within a minute, could have it been tighter, I'm not sure, could I care, NO, this rifle was going to do everything the kid needed and some.

I built my own dasher on a defiance, nitride, 27" Hawk Hill marksman, Manners T4A mini, new Kahles 5-25i, it printed 1.5" at 1L, the 4th shot skipped 1.5" right, was windy, shot one more group, 2.5" but way lower right, it is still a work in progress. I am using RL 16 and experiencing the usual blowback into the chamber that I've seen on every rifle using 16, so much so I pulled my tbac 6.5 ultra and am running a 419 brake till I can get into fired brass totally.
I'm not tying in the least to be an ass to you, but I know more about load dev and barrel harmonics, and even barrel contours to when they work in a guys favor.
I may be repulsive to you, but I try to make some of these new guys think they have figured it out on their own with a slight amount of guidance, so if my tidbits are not enough, sorry. It takes a different person these days to put faith in someone they do not know, but still ask for blind advice. I've taught a lot of younger guys to reload, and think I've did ok, but lately I'm getting feedback that they now need their ammo to work in the rain, wet ammo, OMFG, I'm out.

 

[MarinePMI]

I think Culpepper is right (as others) in that the data points are not nearly robust or numerous enough to draw any conclusions on whether it is a velocity plateau. That being said, velocity is not always a linear increase when compared to charge weight. This has bee seen before, but usually in smaller, "sub-caliber" cases (.17AH, 17 Mach IV, 20 VT, etc.). The leading theory is it has to do with ignition, case/charge volume, bore volume and the retardant that is put on the powder. In that, at some point, due to the retardant's characteristics, it can not physically burn at a rate sufficient to increase velocity. But, at some point as it moves down the barrel, and the powder diffuses, it can suddenly reach a air/powder ratio where it can suddenly flash burn, dramatically increasing pressures, while not actually increasing the velocity of the bullet the burning gases are pushing against. At some point, when powder is continually added, that flash burning will exceed safe pressures and something will give (usually the case or primer, in some cases, the firearm).

Lil-Gun is a well known powder that exhibits this behavior, specifically in the .22 Hornet, where the powder charges are increased, and at some point the velocity flattens, regardless of how much powder is increased...and then spikes. Violently. (This is evident and demonstrated with a change in cases, which vary widely in case volume capacity between manufacturers.)

If working up a load, and a clear and defined plateau of velocity is reached, be very cautious. Physics are physics, and that energy that may be getting blown out the muzzle as a flash of half burned grains of powder, may suddenly reach a point of combustion that is still contained within the barrel. The energy is always there, but it has to go somewhere. Bad ju-ju usually follows if you try and push past a velocity plateau with these newer powder coatings.

JMTCW...

Edit: Just to add, I have never heard of this happening with a longer, cylindrical powder before. I'm not sure if what I have seen and posted is specific to spherical or finer grades of powder or not, but mention it for the sake of discussion.

 

[Milo 2.5]

I think Culpepper is right (as others) in that the data points are not nearly robust or numerous enough to draw any conclusions on whether it is a velocity plateau. That being said, velocity is not always a linear increase when compared to charge weight. This has bee seen before, but usually in smaller, "sub-caliber" cases (.17AH, 17 Mach IV, 20 VT, etc.). The leading theory is it has to do with ignition, case/charge volume, bore volume and the retardant that is put on the powder. In that, at some point, due to the retardant's characteristics, it can not physically burn at a rate sufficient to increase velocity. But, at some point as it moves down the barrel, and the powder diffuses, it can suddenly reach a air/powder ratio where it can suddenly flash burn, dramatically increasing pressures, while not actually increasing the velocity of the bullet the burning gases are pushing against. At some point, when powder is continually added, that flash burning will exceed safe pressures and something will give (usually the case or primer, in some cases, the firearm).

Lil-Gun is a well known powder that exhibits this behavior, specifically in the .22 Hornet, where the powder charges are increased, and at some point the velocity flattens, regardless of how much powder is increased...and then spikes. Violently. (This is evident and demonstrated with a change in cases, which vary widely in case volume capacity between manufacturers.)

If working up a load, and a clear and defined plateau of velocity is reached, be very cautious. Physics are physics, and that energy that may be getting blown out the muzzle as a flash of half burned grains of powder, may suddenly reach a point of combustion that is still contained within the barrel. The energy is always there, but it has to go somewhere. Bad ju-ju usually follows if you try and push past a velocity plateau with these newer powder coatings.

JMTCW...

Edit: Just to add, I have never heard of this happening with a longer, cylindrical powder before. I'm not sure if what I have seen and posted is specific to spherical or finer grades of powder or not, but mention it for the sake of discussion.

I think you are referring to the upper end of the spectrum and are spot on there. But there can be flat spots while increasing powder charges and going over them is more than safe. There is enough data out to know if you are within reason, even considering all barrels react in their own fashion.
The 6 Br case where at times a .2gr of powder can mean a 4K increase in pressure when approaching the upper limits come to mind, like your example of 22 hornet.