I didn't keep a record my groups but shot 1/2 of the testloads and plan to reload again. I write my weights on my brass with a sharpie but some smeared. When I reweigh the brass I'll submit my findings. However I don't plan to reload until I purchase a replacement Lee Neck sizing die. I got too much runout using my standard dies compared to last time when I used my old Lee neck sizing collet die.
Questions about Weight-Sorting Cases
- Thread starter South Pender
- Start date
I cannot claim that weight by volume vs weight by volume makes a difference from my 7.7x58 case separation. I was trying to limit variation to find the most accurate load for now. The only thing I could infer from my last test results was that my groups changed as the length changed. My groups were tightening.. Still I have to retest. A constant strong wind picked up across the range for my last string of test loads and I printed a nice a horizontal string holes.
There are a bunch of variables in bullet accuracy. Case weight is probably one of the least well correlated with precision. That was my point. Do you use brass only one time as well?
John
With case weight to volume correlation questioned by many, I can see your point.
Case volume, percent of fill, some even shooting over 100% fill, volume just seems to be a little important.
Those that load to 80% fill case it probably won't matter. It's just empty space.
Measure powder to +/- a tenth of a grain (good enough?) case weight/volume won't be seen on target.
Most will shoot like headstamps/years because brass matters. Mixed brands/weights do seem to matter. Lapua is called out because it is good and closely matched (I can't because not available for my cartridge).
Seems neck tension and nothing else really matters.
If you take great care with most steps in reloading and seem to be stuck breaking 1/2MOA for groups then practice more, improve wind reading skills, but if charge density matters (case volume) just a little, and it's pretty much FREE. WHY NOT?
Even a gain of 1/8 MOA would be welcome for the minor effort required.
I will repeat what I said in an earlier post;
Most weight to volume tests and charts are not precise enough to determine correlation.
Volume changes from virgin, sized, once fired, sized and fired again. That matters to some.
Case volume, percent of fill, some even shooting over 100% fill, volume just seems to be a little important.
Those that load to 80% fill case it probably won't matter. It's just empty space.
Measure powder to +/- a tenth of a grain (good enough?) case weight/volume won't be seen on target.
Most will shoot like headstamps/years because brass matters. Mixed brands/weights do seem to matter. Lapua is called out because it is good and closely matched (I can't because not available for my cartridge).
Seems neck tension and nothing else really matters.
If you take great care with most steps in reloading and seem to be stuck breaking 1/2MOA for groups then practice more, improve wind reading skills, but if charge density matters (case volume) just a little, and it's pretty much FREE. WHY NOT?
Even a gain of 1/8 MOA would be welcome for the minor effort required.
I will repeat what I said in an earlier post;
Most weight to volume tests and charts are not precise enough to determine correlation.
Volume changes from virgin, sized, once fired, sized and fired again. That matters to some.
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ronemus
Gold $$ Contributor
As pressure builds, the case wall is pressed to the chamber wall well down the case, probably to just above the case head, and the head is driven to the bolt face; I consider that the relevant volume of the case, not the volume after spring-back. The void in the extractor groove and between the case head and chamber wall are the only voids when the cartridge is fired.
I did an experiment several years ago to determine just how much effect brass weight has on .223 loads. I used WW brass (sized, trimmed and deburred, primer pockets uniformed, flash holes deburred, and neck turned) , WSR primers, charges of RL-15 or N-550 powder weighed to 0.1 gr, and 75 gr A-Max bullets. Using the lightest and heaviest cases (sorted from 1000 once-fired I had on hand), I had two lots of 10 cases with a 3 gr difference in weight. The average muzzle velocity difference was 16 fps, just a bit more than the 12 fps due to 0.1 gr of powder. I choose to sort 0.5 gr lots of .223 brass for my long range loads, but the effect will only matter at 800-1000 yards - the vertical displacement on the target from such a small velocity change is negligible at shorter distances. Unless you control all other sources of variation, the effect of brass weight is negligible. I also shoot .284, and because the brass is twice as heavy I batch in 1 gr lots.
I did an experiment several years ago to determine just how much effect brass weight has on .223 loads. I used WW brass (sized, trimmed and deburred, primer pockets uniformed, flash holes deburred, and neck turned) , WSR primers, charges of RL-15 or N-550 powder weighed to 0.1 gr, and 75 gr A-Max bullets. Using the lightest and heaviest cases (sorted from 1000 once-fired I had on hand), I had two lots of 10 cases with a 3 gr difference in weight. The average muzzle velocity difference was 16 fps, just a bit more than the 12 fps due to 0.1 gr of powder. I choose to sort 0.5 gr lots of .223 brass for my long range loads, but the effect will only matter at 800-1000 yards - the vertical displacement on the target from such a small velocity change is negligible at shorter distances. Unless you control all other sources of variation, the effect of brass weight is negligible. I also shoot .284, and because the brass is twice as heavy I batch in 1 gr lots.
6bra1k
Banned
do you shoot 1000 yd br ???
6bra1k
Banned
if your gun only shoots 1/2 moa, you should not be in this conversation. 1/4 is the starting point for long range.....
OK Dokie.
But, once i get brass weight sorted (volume), charged to +/- 0.04 grains, and my primers sorted,
I'll Be Back
But, once i get brass weight sorted (volume), charged to +/- 0.04 grains, and my primers sorted,
I'll Be Back
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The theory says you should sort based on volume. I sort trimmed brass based on weight and I assume 0.3gr variance. Out of 1 Lapua box I usually end up with 3 lots of about 25 cases (which is what I need for a single match). The outliers are used for training.
Did you adjust the scope or not use the same point of aim for these groups?
And I have an observation that may be relevant. I have seen pressure go up with the same charge in neck size only brass that was a very close fit to the chamber when compared to the same load with full length sized brass that has some wiggle room in the chamber. I think Stretching the brass removes some energy from the system and acts as a slight pressure dampener. I do not think this is the case if you're full length sizing leads to compressed charges with the same mass of powder. At that point I think it does more to add to the pressure than it helps.
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Okay, great question.
That picture of two groups was actually one group. It was shot round-robin.
In other words the bullets are colored with a sharpie. All rounds shot at he same target, alternating between colors. The goal is to "even-out" or "level" the atmospheric conditions, so as to better see the one change (case-weight) in the test.
I hope this helps
CW
Very nice methodology. That is exactly as it should be done. Interesting to see the difference in average point of impact height between those sets.
How did you process this brass? Sizing die type, other dimensional controls such as trimming turning ect, and when in that process did you weigh them?
dgeesaman
Gold $$ Contributor
I did the exercise of sorting brass by weight, by internal volume, and by both. 6BRA and Lapua brass.
I found no correlation to velocity. That’s not to say it cannot exist, and surely with enough variance it will, but in my experience it’s a fairly fine variable and it’s effect can be negligible in many cases.
David
6bra1k
Banned
what was your weight separation..in grains
dgeesaman
Gold $$ Contributor
It was Peterson 6BR brass, not Lapua. 133.75 min 135.3 max. Water volume ranged from 37.77 to 38.02 gr.
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