Variations in.223/5,56 brass

[wmitty]

Using range pickup brass to form into .222 Rem and learned the hard way about weight (case volume) variation. I’m now sorting cases by weight and loading a batch of similar weight cases (one grain spread) and am wondering if this is too conservative. Weight of brass varied from 88 grains to 101 grains. Would loading a batch of cases over a three grain range cause significantly higher pressures in the heavier (smaller volume) brass?

[DonMountain]

After sorting through the same problem with range-pickup brass for my pistols and rifles for years, I have come to the conclusion that junk brass results in junk loads. If you want loads that produce similar accuracy's, pressures and velocities with the same primers and weights of powder and projectiles, then you also need brass purchased from the same manufacturer at the same time. Pistol brass in particular have way different internal volumes that result in far ranging bullet velocities. Precision rifle loads need precision selection of casings. Thats not to say that you can't acquire used idendical brass. I purchased a thousand Lake City 5.56 NATO brass all of the same year with very close weights from a supplier. But you can't pick them up at a public range like that.

[country gent]

You might try sorting by head stamp first and see if that tightens it up some rather than the tedious weight sorting. I also believe one lot of brass all the same lot number is best. Bass can be sorted in several ways weight, neck thickness, and neck concentritiy.
Weight, while all the same weight is the brass the same or is it thinner on sides and thicker base?
Neck thickness, does .001-.002 in the neck make a big difference?
Neck concentricity, wall thickness around the neck varying by more than .0004. Some claim this is an indication or the bases being out also and since brass thicken towards the head a bigger concern.
Some also check for the heads being square to the bodies centerline.

For 222 it is getting harder to find now forming from 223 is viable and can be done. There are several areas than can cause pressure increases with the cases from the forming process.
1) Where the brass is was located Sizing down 223 to 222 part of the new cases neck is formed from the 223s shoulder and may be to thick
2) walls may be thicker on 223 cases in the body area
3) the new case may need to be fire formed with a lighter load first time to get its true form and capacity.

I have sized down 223 to 222 and its some what straight forward. A gage or ball mike should be used to check the new necks thickness. After sizing annealing the case necks may help with case life also.

As to range of weight 88-101 grns means a 94.5 grn mean so .95 grns is 1% variation your in the ball park there. As a simple test to see what effect it has weight 10 cases all the exact same then 10 cases 2 grns =/- 1 grn ( 5 of each). Load with firearms best load as tight as you can. Shoot one group and take a break then shoot the second. A plus would be to have a friend or someone hand you the unlabeled rounds with you not knowing which was which. If your theory is correct the 10 identical rounds should shoot a nice round bug hole. The 10 with cases +/- 1 grn should shoot into 2 5 shot bug holes.