Weighing bullets

[GaCop]

Well I see Mike's back to being his old "If you're not doing it my way you're doing it wrong" self again. :thumb::hail::tea:

[mikeinco]

well ladies and gentlemen,
if you are going to attack me...hmm i thought management said you could not do that, at least tell me what you are talking about. at least 2 different subjects here.


Well I see Mike's back to being his old "If you're not doing it my way you're doing it wrong" self again.

[wbm]

Well I see Mike's back to being his old "If you're not doing it my way you're doing it wrong" self again.

Lol! Yeah! Homozygous for the trait.

[charlie b]

This has all been made a bit more curious to me after doing some shooting.

First, cast bullets, weighed and sorted in tenth grain increments and then shot at 100yd. Total variance was 2grains (175 to 177) Virtually no difference could be seen in POI. The biggest difference was when I shot a group of rejects, mostly low weight (172-174gn) and they produced a scatter. To be expected, IMHO, since the low weight indicates possible voids and probably off center. These were all with a weighed powder charge of 23.8gn of IMR 4198.

Second, I had my trusty Axis in .223 with 77gn SMK's. This rifle, in my hands, is around .5MOA out to 600yd. I was testing the effect of using charges thrown directly from my Lee powder measure. I sorted cartridges by weight. From 23.2 to 23.8 gn of Varget. At 300yd the groups overlapped almost perfectly.

So, I did some more research and turned up this gem of a video. The guys here take two rifles (6x47 Lapua and 6.5CM) and test the ability of different powder measures to produce desired charges.

https://www.youtube.com/watch?v=mqvbG2hzUgM

It can be a bit of a chore but if you study the spreadsheets you will note that velocity varies when charges are equal by 10 to 20fps. If you check the velocity difference for a 0.5gn change in powder it shows 10-20fps change. Basically the charges thrown by the Harrell powder measure were very close in velocity deviation to the more accurate charges measured by the automatic units. Group sizes at 600 were a bit intetesting as well, especially the Lapua. The thrown charges were just as or more accurate than the automatic charges even with higher charge standard deviation. I am not as forgiving as the testers, who ;threw out' fliers. The important part of this test is the fliers as they 'should be' the entire issue of the test, ie, what is the worst variance of the tested powder measures.

The other good news is that my cheap Lee powder measure throws almost as consistent charges as the Harrell. FWIW, my loading technique is to throw a charge and measure it. If it is the weight I want I load it. If not I put it back in the hopper and throw another charge. I find that technique faster and less frustrating than using a trickler.

And, no, I do not recommend that very long range precision competition shooters should change what they are doing. If what you are doing works for you then stay with it. These are just my observations for purposes of my shooting.

I would like to see other people do some controlled testing of bullet weight and powder charge weight variations.

[charlie b]

PS just for grins I played around with a ballistics calculator.

.338 Lapua Two cases. 10fps change in muzzle velocity. At 2000yd it results in 14" change in POI. At 1000yd it is just under 2". At 600yd it is 0.5". At 200yd it is 0.03".

[mikeinco]

while your opinion is great, and you are shooting savage rifles, this si great in the hunting world.
it will not get you far in the precision target world not even in f class.

your cast bullet test...sierra uses plus ot minus .3 on their bullets. i would expect bullets that weigh the same to shoot well. groups that weigh close will also do well.

as for your lapua 10 fps "data" try the real world. go to a 2000 yard match. the record for 5 shots is just over 14". most are no where near 14.

[charlie b]

I agree. I do not expect to be able to shoot F class alongside people using custom jacketed bullets or even good commercial match bullets. I got over the need to compete many years ago. My goal is a kinda dumb one. Just pop soda cans at 600yd on a regular basis. I won't mind the odd 'flyer' but a 75% hit rate or better would suit me.

One thing that started this was determining the effect of bullet weight on performance. FWIW, bullet weight has little bearing on external ballistics, but, it does affect the muzzle velocity as the force it takes to accelerate the bullet differs. The consistency can be an issue if the bullet is 'lopsided' due to the difference in weight.

Sorry I misread your post so am revising this part.

The .338 data kinda surprised me. Combined with the data on powder measures and resultant velocity it seems that we might be better off with charges measured by volume instead of weight.

I was a test engineer on high power laser systems for many years so this kind of stuff is what I live for :) More data is always better.

[mikeinco]

generic answer
basically all mil and commercial ammo is loaded by VOLUME....CAUSE THAT IS HOW THE MACHINES WORK.
in the real accurate part of rifle shooting no one uses volume, all use very precise weight....as in .02 or .01, some but do use .1.
short range br would be an exception, but they use VERY PRECISE VOLUME measurements.



I agree. I do not expect to be able to shoot F class alongside people using custom jacketed bullets or even good commercial match bullets. I got over the need to compete many years ago. My goal is a kinda dumb one. Just pop soda cans at 600yd on a regular basis. I won't mind the odd 'flyer' but a 75% hit rate or better would suit me.

One thing that started this was determining the effect of bullet weight on performance. FWIW, bullet weight has little bearing on external ballistics, but, it does affect the muzzle velocity as the force it takes to accelerate the bullet differs. The consistency can be an issue if the bullet is 'lopsided' due to the difference in weight.

Sorry I misread your post so am revising this part.

The .338 data kinda surprised me. Combined with the data on powder measures and resultant velocity it seems that we might be better off with charges measured by volume instead of weight.

I was a test engineer on high power laser systems for many years so this kind of stuff is what I live for :) More data is always better.

[charlie b]

I don't want to take this away from bullet weight contribution to accuracy so will leave this for now. If I get some more experimental data that seems pertinent I will start another thread. Sorry.