Weight spread sorting magnum cases

[Davidb187]

Hello gentlemen,
I'd like to sort 300 Win mag cases by weight for a long range rifle. How much weight spread do you find acceptable sorting a big case like 300wm?
1gr? 2gr? I've got a good stash of PPU cases that's all over the place. No good. Surprisingly REM cases are better weight wise.
I'm juste experimenting as i have Peterson brass too.
Sorry for the bad English. Not my main language.

 

[Straightshooter1]

Hello gentlemen,
I'd like to sort 300 Win mag cases by weight for a long range rifle. How much weight spread do you find acceptable sorting a big case like 300wm?
1gr? 2gr? I've got a good stash of PPU cases that's all over the place. No good. Surprisingly REM cases are better weight wise.
I'm juste experimenting as i have Peterson brass too.
Sorry for the bad English. Not my main language.

Maybe this'll help ¯\_(ツ)_/¯. . . .

In the picture below I sorted a box of 100 Lapua .308 brass by weight. I took 5 of the lightest and 5 of the heaviest, loaded them up the same and fired them to see what the difference was. Well, there was a significant difference in their ES between them (like ~ 60 fps). Then I took, from what was left, 20 of the lightest and 20 of the heaviest and likewise loaded them up and fired them. Both the lightest batch and heaviest batch produced ES's under 20 fps with very low SD's. And when I compared the velocities of the initial 5 lightest to the next batch of 20 lightest, there was no discernable difference.

What I took away from my little experiments is I don't want to mix the lightest with the heaviest, which was 2gr difference for these .308's. That 2grs represents ~1.2% of the average weight. If you're average weight is say at 249 grs, you don't want to have 3gr difference and I wouldn't want 2grs either. So, I'd suggest sorting to 1gr batches would do well.

Also, you I found likewise that sorting primers by weight can make a significant difference. If I had to choose between sorting brass by weight and sorting primers by weight, going with primers sorting is my choice.

 

[Bronsin]

With the .300WM cases, I suggest sorting by case wall thickness first. The easiest way without getting a specific tool for it is to see how banana shaped the cases are after fireforming. .002 or more gets parked. They will throw fliers like there's no tomorrow. If they survive that test, then try sorting by weight. A half grain is plenty close, and may be smaller than you can get anyway.

 

[358WCF]

Sorry for the bad English. Not my main language.

Your English is better than many native English speakers.

 

[Davidb187]

Your English is better than many native English speakers.

Thanks. When reading it's good but writing .. Let's just say i don't practice enough.

 

[Steve Donlon]

Maybe this'll help ¯\_(ツ)_/¯. . . .

In the picture below I sorted a box of 100 Lapua .308 brass by weight. I took 5 of the lightest and 5 of the heaviest, loaded them up the same and fired them to see what the difference was. Well, there was a significant difference in their ES between them (like ~ 60 fps). Then I took, from what was left, 20 of the lightest and 20 of the heaviest and likewise loaded them up and fired them. Both the lightest batch and heaviest batch produced ES's under 20 fps with very low SD's. And when I compared the velocities of the initial 5 lightest to the next batch of 20 lightest, there was no discernable difference.

What I took away from my little experiments is I don't want to mix the lightest with the heaviest, which was 2gr difference for these .308's. That 2grs represents ~1.2% of the average weight. If you're average weight is say at 249 grs, you don't want to have 3gr difference and I wouldn't want 2grs either. So, I'd suggest sorting to 1gr batches would do well.

Also, you I found likewise that sorting primers by weight can make a significant difference. If I had to choose between sorting brass by weight and sorting primers by weight, going with primers sorting is my choice.

View attachment 1749390

Did you turn the necks?

 

[Straightshooter1]

Did you turn the necks?

Yes. I always turn my necks. . . typically to .014" for my .308's.

The necks for those in that picture were turned and cases trim length and shoulder bumped to within +/- .0005" of each other. I wanted to be sure those particular dimensions didn't have much effect on the case volumes.

 

[mgunderson]

From the sounds of the brass it might not be all the same lot. Weight might be a reasonable indicator of the same lot. If you have a big volume of cases..... I recommend a tighter selection.

I like to weight sort brass. The heaviest and lightest are used for set up cases. Found some interesting anomalies after cases of different cartridges. I also visually inspect each case at this time. Keeps my squirrels in line too.

 

[ronemus]

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.

 

[dryhumor]

I sort out batches by .1-.2 grain. If I can’t get enough to make it worthwhile, I increase the range to .4-.5 grain spread. I still use the ones that are lighter and heavier, but as foulers or practice.

I think getting a 100 or more in the same lot gives you better results in sorting. OTOH, if a hunting rifle, you really only need a few cases the same weight to last quite awhile.

 

[mmcu]

I weight sort my 270 WSM brass to +/- 0.5 grains with good results.

 

[Steve Donlon]

Maybe this'll help ¯\_(ツ)_/¯. . . .

In the picture below I sorted a box of 100 Lapua .308 brass by weight. I took 5 of the lightest and 5 of the heaviest, loaded them up the same and fired them to see what the difference was. Well, there was a significant difference in their ES between them (like ~ 60 fps). Then I took, from what was left, 20 of the lightest and 20 of the heaviest and likewise loaded them up and fired them. Both the lightest batch and heaviest batch produced ES's under 20 fps with very low SD's. And when I compared the velocities of the initial 5 lightest to the next batch of 20 lightest, there was no discernable difference.

What I took away from my little experiments is I don't want to mix the lightest with the heaviest, which was 2gr difference for these .308's. That 2grs represents ~1.2% of the average weight. If you're average weight is say at 249 grs, you don't want to have 3gr difference and I wouldn't want 2grs either. So, I'd suggest sorting to 1gr batches would do well.

Also, you I found likewise that sorting primers by weight can make a significant difference. If I had to choose between sorting brass by weight and sorting primers by weight, going with primers sorting is my choice.

View attachment 1749390

Yes. I always turn my necks. . . typically to .014" for my .308's.

The necks for those in that picture were turned and cases trim length and shoulder bumped to within +/- .0005" of each other. I wanted to be sure those particular dimensions didn't have much effect on the case volumes.

Thanks, I just bought 300 Lapua 6mmGT cases and I better sort them into 3 separate lots from what you have found out. Never would have figured they would be so far off. I would have assumed neck turning would have been good enough.

 

[Straightshooter1]

Thanks, I just bought 300 Lapua 6mmGT cases and I better sort them into 3 separate lots from what you have found out. Never would have figured they would be so far off. I would have assumed neck turning would have been good enough.

Another thing I did was measure the thickness of the webs using a pin gauge. The average thickness was .1801". Most of them were within .001" difference. But there were just a couple that were substantially more, like thickest at .1840" and the thinnest at .1775". . . . 0065" difference. In these particular two cases the difference in the thickest and thinnest had a case weight difference of 1gr. The difference in web thickness doesn't always directly correlate difference in case weights.

Just thought I'd share that since you mentioned neck turning being a factor. A lot of things going on with the brass distribution through out a case given how cases are formed from brass cups.

 

[ELR LVR]

I sort my 284 cases within 3 grns of each other
but also sort my primers to within 3 Milligrams
---
results are consistent 1/2 MOA or better at 600 yds (3 inch groups @600)
I see more horizontal usually than i do vertical, which is probably me using a bipod
H1000 powder seems very consistent and is a good powder for 300 WM

 

[Davidb187]

Thank you very much for yours insight.