Trickymissfit
Well-Known Member
the reason a case shrinks when fireforming an improved case is that the neck follows that path of least resistence. There's less metal there to fight the pressure build up when moving metal to fill the voids created in the chamber with an improved reamer. Normally your looking at .03" to .04" in neck shrinkage. I used to know one guy that had a short barrel with the same chamber as his longer barrel (.243 Ackley) but with a little longer neck. He formed his cases from 6mm Remington brass. After fire forming he then trimmed the cases to 2.04" from about 2.06" after fire forming. Incedently the 6mm brass moved about .045" of brass out of the neck verses about .03" for the 243. This fell right in line with Ackley's thoughts on the .308 case, as there was little to be gained other than stopping brass flow. Why did Doug go with 6mm brass instead of simply using .243 brass? Case and barrel life were better.
gary
gary
