.40 Barrel Speed Differences

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NH_Pilot

New member
A question for the brain trust.

From reading a number of opinions about loading pistol cartridges, it appears that pistol shooters look for a minimum speed (power factor) and comfortable recoil, not talking a lot about stats like ES. Am I guessing correctly that the shooter is a much large factor than the ES and SD of a load?

I am reloading .40 using 165gn Berrys copper plated flat points over 6.3gn VV N340. Works good and actually makes this shooter look good.

The press is a Hornady Lock-N-Load Progressive with Lee dies.

Yesterday I chrono-ed the load using two different pistols and was surprised at the results.

My HK USP .40, 18 shots, has a high of 1070, low of 1018, average of 1054, ES 52.

My wife's Sig P229, 10 shots, has a high of 1054, Low of 1027, average 1040, ES 27.

It is interesting that the Sig barrel is slower, but I was really surprised that the ES of the same lot of cartridges shot through the Sig was nearly half of the ES of the cartridges shot through the HK. I was under the impression that ES had more to do with the consistency of the reloader. Is this suggesting that a little more powder and pressure will result in decreased ES overall?

The load works well, I do not need more speed, the wife already shoots better scores than I, and I could not make a sample batch and get to the range with the chrono for another week anyway,so I thought that I would throw the question about barrels and ES out for comment.

Thanks!

Wes
 
G

g.willikers

New member
It's a confusing world.
There's so many variables in guns and ammo, that it's not surprising to see such differences that you describe.
From variances in barrels, rifling, chambers, how the powder packed in the cases, bullet fit in the cases, and on and on.
 
S

SL1

New member
Actually, those velocity data are pretty good. The ES is not bad for pistol cartridges, and the difference between average velocities for the two guns is relatively nothing. You should see the 200 fps differences in average velocities among revolvers with the same barrel lengths and same loads on the same day. Those data would definitely make you feel good about your load.

Another point to consider is that you are comparing the extreme spread for 10 shots against the extreme spread for 18 shots. Note that the low value for your HK was lower than the low value for your wife's SIG, and your high value for your HK was higher than the high value for your wife's SIG. If your wife had shot 8 more rounds, it is likely that her high and low values would be somewhat closer to yours. There is also a chance that the average velocities would get closer together, considering that the mid-points in your extreme spreads are 1044 fps and 1040.5 fps, respectively, which is only 3.5 fps difference, compared to the 14 fps difference in the averages.

It is usually better to work with SDs instead of ESs when comparing loads, which helps deal with different numbers of shots.

But, it is simply not worth the effort in this case, because the load is not showing anything worth worrying about in either gun.

SL1
 
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N

NH_Pilot

New member
Thanks for the insights! A sanity check on your work is always a good thing.

For what its worth, the P229 has a 3.9" barrel and the USP has a 4.25" barrel.

Now I just have to make sure that I hold the pistol in the correct hand and shoot the correct target at the local fish & game club's version of action pistol.

Wes
 
S

Sevens

New member
Before I tried to make ANY conclusions from the short bit of data we've got, I'd point to how much data you've got. If we are talking about a short handful of shots, I don't take a lot of stock in it.

That's the #1 gripe I have about my particular brand of chrono. (actually, I have a lengthy list of gripes about my chrono, but...) The ignorant thing limits me to 10 shots in a string.

ANY "experiment" is going to come to a much more solid, tangible conclusion when you REALLY give it the go. If I shoot a 10-shot string and my ES or SD is freaky and wild, I know that I've got a load that isn't ever going to give me low ES or SD.

If you think you cured some kind of mouse cancer with a medicine, you'd really want to cure 400 mice instead of 3 mice before you ran to the world with your shocking discovery.

If I shoot a 10-shot string with a crazy low ES & SD, I wanna shoot another, and another. And I have to keep shooting strings... because I'm -FAR- too stoopid to do the math that would put 30, 50 or 75 shots in to one string, and my idiotic Canuck chrono only lets me put 10 shots in a string. :mad:

I have confidence in coming to negative conclusions with 10-shot strings when things don't ring up impressive numbers.

I definitely hesitate to come to positive conclusions in 10-shot strings when they do. I suppose I want more proof.

I also want a different chrono.
 
S

SL1

New member
I used QuickLOAD to estimate the difference in velocities that could be expected from your load, assuming that EVERYTHING else stays constant between two guns. Adjusting the case volume slightly to give 1040 fps with a 3.9" barrel and then changing the barrel length to 4.25 produced a velocity result of 1061 fps. So, your 14 fps difference between your two guns is actually a bit less than one would expect for the differnce in barrel lengths, alone.

But, there are probably other differences besides barrel length at work, as well as the fact that the small sample of rounds produces significant uncertainty about the exact difference in average velocity between your two guns.

SL1
 
W

WESHOOT2

New member
to any who can

Take many like-length guns to the chrono and shoot same-lot ammo.
You will likely find a great discrepancy between fastest and slowest.
 
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