Does The Case Brand Matter?

When I shot active service rifle competition I loaded thousands of rounds of .30-'06 and 7.62mm ammunition for 200 and 300 yard rapid fire practice and also for infantry trophy. Mixed headstamp cases were used, as long as they were “GI” cases.   Ordinary Ball M2 or Ball M80 cases were OK, as long as you did not use any which had been fired the first time around in machineguns.  Firing in an MG sets the shoulders back due to over-ramming and increases headspace.

Fired brass was all full length resized, trimmed and deburred 100% no exceptions.  After sizing, trimming and deburring, cases were tumble cleaned in ground corncob, and primer pockets uniformed in a drill press using a White Tail Engineering tool with fixed depth stop, then visually inspected during priming.

Priming was done by using a hand primer seater which enabled you to “feel” loose pockets and reject those cases.  Powder charging and bullet seating was done on a Dillon RL550 using a Lyman M type step expander die, measuring charges of WW748 or 4895 powder and seating pulled GI M118/M72 match bullets left over from making “Mexican Match."  This is when you pull the GI bullet from arsenal ammo and replace it with a 168-gr. Sierra over the original powder charge, which we comonly used for team match ammo.

Over the years I probably assembled 100,000 rounds of reloaded practice ammo. For the most part these reloads would equal the grouping of statistically average lots of M118 Special Ball from an accurized service rifle, either M1 or M14.

When I started shooting cast bullets in bolt action military rifles for reduced National Match Course I followed essentially the same practice, substituting lubricated, cast bullets and appropriate charges of RL-7 or #2400 powder, dropped in blocks of 50 at a time  using a Culver measure, and doing final assembly on a single stage Huntington Compact press, since I didn't need mulitiple thousands of rounds.

The only concession to accuracy was check-weigh empty prepped brass to eliminate “heavy” or “light: ones, sorting into batches color coded using a felt tip marker acroiss the headstamp, by weight so that all was within +/- 1 grain within a batch.  Headstamp didn't matter. I checked neck wall thickness of loaded rounds 100% using ring gages after bullet seating.  Any “fat” necks larger than .340", but smaller than .346” were sorted for use in my M1917 Enfield, rather than my tighter Smith-Corona 03A3. Anything over .346” loaded cartridge neck diameter when using a .311” cast bullet was pulled down and the case necks turned to 0.011” wall thickness and kept as a separate batch.

As long as cases are full length sized and weight the same, their powder capacity is the same. Given the difference between the specific gravity of typical powders, about 0.85 grams/cc and the density of cartridge brass, it takes about a 12 grain difference in case weight to equal a 1 grain change in powder capacity. In cases the size of .308 Win. or .30-'06 a 2 grain extreme spread in case weight doesn't matter. But in small cases such as a .222 Rem. or hornet which would use a much smaller charge, then it does.