When weighing cases; what is the range that I should keep in a bundle? In .308 I have a range of casing weights from 150.6 to 170.5 (50 cases). How do I cull?

I used to do this. The result and improvement was a total ZERO.

Personally, I would load all this brass and forget about it.

gotta agree with that.........personally I believe that barrel quality, ammo consistancy, shooter ability and a few others factors are far more important than case weight.
Back when I worried about such things I would seperate them based on statistical deviation.....meaning take the spread from heaviest to lightest and break down the grouping based standard deviation. its called SPC.............

mose that is quite a spread. are they mixed head stamps?
I usually get about 2grs +or- with win. and rem brass.
if they are mixwd i would sort by head stamp first.
if there from the same lot i would think tht there is a problem either with the brass or the scale.
Dave

Moses,

Case weight is only half the battle. Case weight in and of itself is MEANINGLESS! You MUST determine the INTERNAL VOLUME of the case and sort accordingly. The allowable tolerance on internal volume is driven by the actual cartridge / bullet combination in use.

ASS_CLOWN

Case weight often determines internal vol. so to some extent it can be important. If this is a match/target rifle, I would split the batch in half. 150-160 in one & 160-170 in the other. THis should give you some piece of mind & possibly a bit more uniformity. Do a test, take 5 case of the same weight, take 5 more w/ as great a spread as possible, & loading them the same, shoot for group, say 3 time each & see if there is any real diff.

Moses, I used to weigh cases and go through any other sort of process I could think of short of casting spells to get all cases exactly the same. Results were simply not worth it. The one thing I found that seemed to make a significant difference was concentricity. Get the bullet correctly aligned in the case and I think you will see more difference than all other things put together. At least that has been my experience. The longer the range the more this seems to matter. Good luck.

I have been reloading for various cartridges since 1977 and have never weighed cases. I just bought a Ruger 77 Mk II RSI in a .308. The last one I had I could never get it to shoot better than 1.75". I know this is supposed to be acceptable. Remember only accurate guns are interesting. By weighing cases I thought I might increase the accuracy potential. I haven't shot this gun yet so I don't know what it is capable of doing.

weighing cases IS MEANINGLESS until they have all been match prepped. Unless they have had the primer pockets uniformed, the flash holes deburred, been trimmed to length, chamfored and deburred case mouths,..and even the high spots turned down on the necks,..then you are weighing UNLIKE objects. They must be uniformed across the entire lot. I just match prepped a bag of win 220swift brass (necks turned, primer pockets, flash holes, trimmed, etc) and in a random sample of 10 cases,..they varied by no more than .3gr's. That shows the concentricity of todays brass once the uniforming has taken place. Internal capacity can be judged after the first firing using the water test,..but with unfired weights like I witnessed,..I think it is probably a waste of time unless the rifle is a strict benchrest rig for the LV and HV as well as hunter class.

With as much disparity as you have in that batch of cases, sorting them WILL make significant difference.

I agree with bits a pieces posted here. First, just weighing the cases gives you a clue as to the internal volume of the case but as has been stated, unless the cases are uniformed to some degree you'll not know where those differences lie. If the outside dimensions are the same and one case weighs more than another, it's obvious there would be internal differences. Like comparing a bowling ball to a fish bowl of the same size.

In larger cases than yours (338 Win Mag) I've found that 17g difference in dry case weight is equivalent to one grain of propellant. In other words, the heavier case will have the smaller internal volume which with the same charge weight will increase the velocity and the pressure when fired. That difference translates into about 50fps velocity and WILL make a difference in accuracy. In your case I guess about 12g difference in case weight would be about the same so sorting WILL help. What you do need to determine is the what effect the difference in dry weight will have to the internal volume of the case and this can only be determined by filling the cases with water and determining the water volume of them. However, about 2g of difference in dry weight makes very little difference in water volume in cases your size. I try to sort my brass to within no more than 1% variance in dry weight in a hunting cartridge and will tolerate up to 1.5%. Beyond that you will see variance in velocity and therefore accuracy, particularly for longer range shooting.

Uniforming the cases AFTER fireforming to your chamber and then sorting by weight will help if your rifle and you are capable of near benchrest accuracy. For the average hunting rifle shooting near 1.5" it may make little difference. If you're trying to squeeze that last .2" difference, then it WILL help.

I'd suggest sorting your brass into lots of no more than about 4g difference initially. If you can't get enough cases with this kind of sort then I'd suggest getting a better lot of brass. Brass does vary in most of your domestic manufacturers. Sometimes to you just have to buy another lot of brass.

mose, I just recently went through 150 rounds of .308 win.
brass min. was 166gr and max. was 169.8 grs. i chose 50 rounds at around 168grs. that is what I had the most of.
the brass had been fl x die resized,trimed to length 2.008"
primer pockets cleaned and uniformed, primer hole was chamfered on the inside, the necks were turned for uniformity and to remove a slight bulge on the neck at about .030thsnds in front of the sholder.necks were resized after anneling with a collet die for uniform neck tension. these were loader with 155gr palma for 1000 yrds. oal was 2.087" no bullet runout. 48.2grs H-380, BR-2 primers
100yrd group 1/2" 300yds 1" 500yds 4.5" 1000yds 9.75"
the brass is now fire formed. hopefully the groups will get better. rifle has a 1:10 twist 24" long barrel.
this may help in you quest to shoot better groups.
your load starts with the brass. that is the foundation for you load and if the foundation isnt sturdy the house will fall down.

Do it if you use brass the range. I found that manufacturers sometimes change their supplier or process and that the same head stamp does not say it is a comparable case.

Within one weight class from the premium suppliers like RWS or Norma I found that the variation is very small, less than 1 grain for a 30/06 case. The difference between weigh classes however was up to 10 grains and resulted in a different POI.

JustC,

Even after match prep case weight can vary significantly without effecting the ACTUAL internal volume of the case. It is the combustion chamber volume (the internal volume of the case) which matters! You MUST weigh the prepped empty case, then fill it with water and weigh it again, then subtract the latter from the former.

Depending upon what the useage is determines the allowable tolerance.

As a for instance. Assuming that in the 308 Win with the bullet and powder selected, 1 grain of powder results in a muzzle velocity change of 70 fps.

So for the following tolerances on internal case volume we would expect muzzle velocity variations of:

0.1 grains ~ 7 fps
0.2 grains ~ 14 fps
0.3 grains ~ 21 fps
0.4 grains ~ 28 fps
0.5 grains ~ 35 fps
1.0 grains ~ 70 fps
1.5 grains ~ 105 fps

So there is the approximate affect on muzzle velocity driven by the variation of case INTERNAL VOLUME. You must determine if those velocity spreads are TOO great for your accuracy expectations. Remember as well, most digital scales are advertised to only be accurate to +/- 0.1 grains (and I have found that digital scales actually GR&R around 0.5 to 0.7 grains!!)

I could post actual expamples proving my point, but it is too much typing (and the non-believers would probably call me a liar anyway) so take it or leave it.

ASS_CLOWN

Ass Clown, thank you for another of you wonderful set of numbers pulled out of your ass. What we need do here is fill your head with water. I suspect it's capacity is very small.

Of far more importance than what a case WEIGHS is where that weight is located. If someone is determined to make their reloading a meaningless trip into insignificanse, they should worry about things like neck thickness and runout etc. The fact one case weighs a few grains different from the other rarely amounts to a hill of beans.

All this case BS is stuff for SERIOUS benchrest shooters...and one need be very anal retentive to get into that. For the hunter, this whole subject is pure BS.

And now I yield the floor back to Ass Clown so he can dazzle us with some more useless numbers in hopes someone will be dumb enough to think he knows anything.