Case weight variability question

[Chris J Spierings]

I have been trying to improve my reloading and accuracy a little bit every time I take on a new project. The latest is a 7mm Mag, worked with Pedersen Precision on a Rem action with a Muller works barrel. Anyway I put 20 rounds through it using Norma factory loads I wasn't impressed with the groups but they weren't horrible for still breaking in about 1" ish.

I have been looking around for new brass and found some ADG. It arrived and looked great, I thought what the heck lets see how consistent it is from a weight perspective. The spread across 50 cases was about 4 grains. For the the heck of it I weighed the once fired Norma brass after it had been deprimed, stainless wet tumbled. It was a little under 2 grains spread.

I was wondering what folks consider an acceptable weight range.

 

[lancetkenyon]

I try and stay within 1gr, but will go to 2gr. Sometimes, unless you are willing to cull brass, that is not possible. Not many people want to buy 200pcs of $2/ea brass, to cull 20-40% to get within 1gr.
ADG is good brass. I haven't found 4gr difference in a box of 50, or even 2 boxes of 50. But it is definitely possible.
I doubt you will see a huge difference in velocities with a 4gr swing in brass weight. That is up to you. If you have 80% that is within 1-2gr, you can keep the other 20% for foulers/sighters and use the 80% for your main loads.

 

[Mikecr]

You shouldn't weigh them, as it means nothing at all.
If you want to match capacities, then fully fireform them and measure capacities directly.

 

[Rardoin]

^^^^What Mike said^^^^ I've weight sorted cases and fired the lightest 10 and the heaviest 10 (straight .284 Win/184 Berger hybrid) at 965yds in near dead calm/no mirage conditions and compared the groups. I no longer waste my time weight sorting brass. Most of the long range competitors I shoot with don't either. If you want to trim all pieces the same length and volume sort it may be worth the effort to cull out outliers but I have not done the experiment because it would involve several hundred pieces of brass and too much time.

 

[Coyote Shadow Tracker]

I use Lapua brass for almost all my calibers. I neck turn, clean the flash holes and primer pockets. Then after the third firing I wet tumble stainless, re-turn the necks and trim for length. I checked for the weight then since they are fireformed, neck turned, flash holes and primer cleaned. They are really close within 1 gr. so I never have done it again as far a weighing. I know Lapua is consistant, but if you really want to get the case accurate you need to do capasity. I try buy good brass of the same lots and trust/hope in the manufacture that each case is the same. weighing is a waste of my time. If you have so many different weights in the brass don't expect to use for "F" class or ELR. However they are just fine for hunting and banging steel.

 

[LRNut]

I have found Nosler to be the most consistent in terms of weight, FWIW. One thing I do is label any case that is markedly heavier (like when I have one or two from a different lot. I can't ever recall missing due to a heavy or lighter case, but then again, my max tolerance is about 2 grains.

 

[Rardoin]

If you have so many different weights in the brass don't expect to use for "F" class or ELR. However they are just fine for hunting and banging steel.

Not necessarily so in my experience (and in the collective experience af many F-open national champions who I shoot with on a regular basis.
Below is unsorted, no turn, no touching flash hole brass score from a recent 1000yd F-class match I shot (10 rind is 1 MOA/ X ring 1/2 MOA):

 

[Coyote Shadow Tracker]

Not necessarily so in my experience (and in the collective experience af many F-open national champions who I shoot with on a regular basis.
Below is unsorted, no turn, no touching flash hole brass score from a recent 1000yd F-class match I shot (10 rind is 1 MOA/ X ring 1/2 MOA):

GREAT SHOOTING! I commend you sir for your accuracy. That is fanatasitic that none of you in your "F" class circle prep your brass and still win championships. I know a lot of PRS shooters that also SAY they don't either. I will be willing to say that you didn't use range brass and different brands of brass just thrown into your reloads? What brass were you using? Do you keep track of each peice of brass for the ammount of reloads, do you mark a peice of brass when that shot is a flier to see ifit was caused by the case? I also know a lot of LR shooters and they use everything in their tool box to get the X. I am myself don't sort as I stated, but do use brass that I have good dconfidence in. I turn necks and cleaning flasholes just to think in my mind it can't hurt -only help. I am not telling someone that is reloading for hunting for a few hunder yards and have a 10" kill zone. What if you are a hunter that is shooting an Elk or Pronghorn at say 800 +yds. would you want to know that your reloads were giving you 1/4" or at the most 1/2" MOA. This isn't paper where if you miss it is alright. Now we are talking about a clean kill of an animal.

 

[Rardoin]

@Coyote Shadow Tracker I don't use range brass. The brass used for the example target was ADG. I don't track brass after the third firing as my measurements show it has reached max form by then. If I get a flier I do mark the case and measure it at several dimensions and use it as a barrel warmer on a subsequent test or match and see if it goes in group. It is the rare piece that I discard because the flier is repeatable. I load for under .3 MOA at 300yds and under 4" vertical at 1000yds on multiple test on different days in calm conditions. I want a load that is capable, under ideal conditions, to put every shot in the 5" x-ring at 1000yds/ 3" x-ring at 600yds. Under match conditions it is the rare day that the load/conditions/shooter all come together to give near .5 moa for all 20 record shots in a string. I've achieved 15x at 1000 and 18x at 600 off of a very solid rest with wind flags. I know I could not achieve nearly that degree of precision with any of my hunting rifles shooting off of a pack or sticks under field conditions with very limited wind indicators.

 

[Coyote Shadow Tracker]

@Coyote Shadow Tracker I don't use range brass. The brass used for the example target was ADG. I don't track brass after the third firing as my measurements show it has reached max form by then. If I get a flier I do mark the case and measure it at several dimensions and use it as a barrel warmer on a subsequent test or match and see if it goes in group. It is the rare piece that I discard because the flier is repeatable. I load for under .3 MOA at 300yds and under 4" vertical at 1000yds on multiple test on different days in calm conditions. I want a load that is capable, under ideal conditions, to put every shot in the 5" x-ring at 1000yds/ 3" x-ring at 600yds. Under match conditions it is the rare day that the load/conditions/shooter all come together to give near .5 moa for all 20 record shots in a string. I've achieved 15x at 1000 and 18x at 600 off of a very solid rest with wind flags. I know I could not achieve nearly that degree of precision with any of my hunting rifles shooting off of a pack or sticks under field conditions with very limited wind indicators.

Sir thank you soo much for your response
Keep shooting th X ring!

 

[Rardoin]

Keep 'em in the boiler room Cotyote.

 

[Barrelnut]

If you take 50 or 100 pieces of brass, number them, and sort them by weight, and then sort them by volume. You will probably find that they sort 85% to 90% they same way. The difference between the 2 two methods is not much and you probably can't tell the difference.

 

[Rardoin]

If you take 50 or 100 pieces of brass, number them, and sort them by weight, and then sort them by volume. You will probably find that they sort 85% to 90% they same way. The difference between the 2 two methods is not much and you probably can't tell the difference.

That is mostly true. However, in the one study where I've seen that done and published, there was not absolute correlation and there were significant outliers that bucked the trend. If not capacity sorting then you have a few black sheep in your 'precisely' sorted group. But I think it is a mute point in that the variables that are, by far and away, the most important to LR precision are not going to be influenced significantly by weight sorting; those variables being the best powder/charge weight/bullet/seating depth. Nail those and you would be amazed how the other minutia many LR shooters spend time on in the load room do not show up on target. I used to do the full Monty of prep with the best tooling available. I no longer use the vast majority of the tools.

 

[Barrelnut]

That is mostly true. However, in the one study where I've seen that done and published, there was not absolute correlation and there were significant outliers that bucked the trend.

I don't think you understand my post. I never said there was absolute correlation. I've run this test on a couple different lots of brass and the result is pretty much the same. 85 to 90% of the cases will sort the same, if you do it by weight or volume. Except for maybe 1 or 2 out of every 10. Those are the "outliers", "black sheep" I believe you speak of. I am also saying that those "black sheep" aren't significantly different by weight or volume to make a difference.
Personally, if I have some brass that's know to have significant weight difference, like Hornady, I usually just weight sort them and take the outliers, that tend to show up on either side of the bell curve, and use them for blinking, etc.