Case Weight and Accuracy???

[4jorgies]

Hello all. I just purchased a Kimber 8400 in 300 Win Mag and then bought 2 boxes of new Nosler Brass. I checked the Lot Number to insure they were the same lot but then weighed them anyhow before dropping them in the MTM box I purchased at the same time.

With my 338 Win Mag I purchased one box of Nosler brass that was all the same weight (+/- .3 grains) and reduced my 100 yard group by a 1/2 inch.

these 2 boxes weigh in at

Box 1 = 214 gr +/- .3 gr

Box 2 = 215 gr +/- .3 gr

all the cases are the same length +/- .005 so that is not the extra gr I am seeing

How much will this affect my accuracy?

This is will be my primary hunting weapon so in realty all I need in minute of deer or moose but there is something to be said for the confidace of knowing you are carrying a sub half MOA rifle when you spot that critter at 400 yards.

[JeffreyDeGraff]

Case weight does affect accuracy. But, In my experience, the larger cases, like 300 win mag, are affected less by small differences in weight than small varmint cartridges. I think you should be fine. You could do a little test and keep the brass separated, work up a load with the lighter brass, then after finding your load, load it in the heavier brass and see how she does. If it were me, I’d just load them, ive got plenty of guns that are .5moa that I’ve never checked the brass


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[Jritt187]

Brass weight has no effect on anything. It is internal volume you want to check. Full length size, trim, chamfer and so on. Do your full case prep, put a plug or old primer in and weigh it. Fill with water and weigh it again. The difference is your internal volume.


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[JeffreyDeGraff]

The general idea is that weight affects volume. Heavier brass typically has less volume.


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[JoeB]

IME, careful case prep has much more effect on accuracy than case weights. I don't weigh them at all anymore.

[JeffreyDeGraff]

[QUOTE=JoeB;3531]IME, careful case prep has much more effect on accuracy than case weights. I don't weigh them at all

I haven’t weighed a piece of brass in over 10 years. Like I said in my earlier post, case volume can be affected by case weight. I have a lot of rifles that are .5 moa or sub .5 moa, that I have no idea how much the brass for those rifles weigh. When I shot bench rest matches in the 90’s, each brass was weighed, primer pockets uniformed, flash holes deburred, necks turned, you name it, but that’s a game where .001” can make or break you. For the average shooter and varmint hunter, brass weight primer pockets and flash holes will make no noticeable difference, but to say that it makes no difference would be wrong. One grain difference in weight on a voluminous case, such as the 300 win mag, is not a huge difference, but it’s still a difference. The OP said that weight sorting his brass on another rifle helped his groups shrink, so why not try on this one?


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[JoeB]

Fair enough.

[handcannon]

I weigh cases then check case volume. Case weight does not give an accurate indication of case volume. Case volume in (my opinion) is where the difference lies. I write the cases weight down then fill cases with alcohol and weigh again. Subtract case weight from gross weight and you have case volume. I keep my case volume within .001 gr. Bullets even though the box says 220 gr not so for all. Bullet weight will vary within a given box. It just depends on how far you want to go with this. Then there's neck turning which centers the bullet to bore adding to accuracy. Sorry got carried away. Oh and the reason I use alcohol is that the residual in the case evaporates rather quickly.

[4jorgies]

First picture is from some load development I did with my brother last year for his 300 at 100 yards

Second pic is the case weight from that group. Did not record which one landed where because weighing them was an afterthought.

Third group was weight matched nosler brass. Same load. 7 shots with scope at max power 3 shots with scope at 4 power.

This is what has me asking about case weight.


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[4jorgies]

End result test at 375 yards

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