I wonder why... Magazine Gun Tests

breamfisher

Looking at some issues of Guns and Ammo I saw that the author had a table with the loading of the bullet, velocity, standard deviation of the velocity, and average group size. In the article he pointed out that the load with the largest average group size also produced the smallest group. It got me wondering: why don't the authors report some metric of the actual variation in group size. Be it standard deviation, standard error, variance, or just the range in group sizes. Seems to me that might be a bit more useful in determining the accuracy and performance of a firearm over the standard deviation of a certain load. In my mind, a load's standard deviation is more dependent on the ammo manufacturer than the rifle manufacturer...

Jeeper

Good point.

Luis

breamfisher

To me, a metric of the variation in average group sizes would be more informative than a measure of the variation in average bullet velocity. The group size variation would give you an idea of not just how small the group is, but how repeatable that is. Just saying the average is, say, 1/2" at 100 yds. doesn't tell the whole story. If that average ranges from 1/4" to 1 1/2" out of 5 groups, is that as good shooting of a load as one that averages 3/4" but the variation is from 1/2" to 7/8"?

Edited to add: for what it's worth, I'm in data analysis mode at work. Can you guess that?

Spk

breamfisher wrote: »

To me, a metric of the variation in average group sizes would be more informative than a measure of the variation in average bullet velocity. The group size variation would give you an idea of not just how small the group is, but how repeatable that is. Just saying the average is, say, 1/2" at 100 yds. doesn't tell the whole story. If that average ranges from 1/4" to 1 1/2" out of 5 groups, is that as good shooting of a load as one that averages 3/4" but the variation is from 1/2" to 7/8"?

Edited to add: for what it's worth, I'm in data analysis mode at work. Can you guess that?

I feel your pain but a lot of folks ain't too saavy in the math stuff. :bang:

I would just tell the authors to print their data and let the readers do their own analysis. I'd be happy with that, just sayin.

JasonMPD

breamfisher wrote: »

To me, a metric of the variation in average group sizes would be more informative than a measure of the variation in average bullet velocity. The group size variation would give you an idea of not just how small the group is, but how repeatable that is. Just saying the average is, say, 1/2" at 100 yds. doesn't tell the whole story. If that average ranges from 1/4" to 1 1/2" out of 5 groups, is that as good shooting of a load as one that averages 3/4" but the variation is from 1/2" to 7/8"?

Edited to add: for what it's worth, I'm in data analysis mode at work. Can you guess that?

Most load info I find in magazines is useless to me for the most part. It's usually used to bolster the advertising for ammo or firearm.

Shoot 1000 rounds of ammo "A" through a test fixture and report the spread and standard deviation. That's more useful to me when seeing how good an ammo is loaded.

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snake284

breamfisher wrote: »

To me, a metric of the variation in average group sizes would be more informative than a measure of the variation in average bullet velocity. The group size variation would give you an idea of not just how small the group is, but how repeatable that is. Just saying the average is, say, 1/2" at 100 yds. doesn't tell the whole story. If that average ranges from 1/4" to 1 1/2" out of 5 groups, is that as good shooting of a load as one that averages 3/4" but the variation is from 1/2" to 7/8"?

Edited to add: for what it's worth, I'm in data analysis mode at work. Can you guess that?

Bream, you raise some very good questions here. But you also might want to remember that a certain load in one rifle might give different results in another one (Same brand and model) just like what is a max safe load in one rifle may be an over load in another. The old adage that every rifle is an entity unto itself holds very true here. I read all this too, and I admit I have tried loads I read about in magazines. But more often than not I didn't get the same results in my rifle. It can be a crap shoot.

NN

They do not report how atmospheric conditions change during their shooting session either; though some do give a general weather report, ie, hot, cold, windy or not.

BigDanS

Personally, for a handgun, I would like to see it put into a Ransom Rest and shot 50 times (one box of ammo ) and report the group size. Smallest group and largest group mean little to me. I need to know if I aim what variance I can expect.

D