.30-06 Ackley -- Thoughts?

[jackieschmidt]

Another fallacy is that the sharp shoulder prevents the case lengthening on firing. Unless there is a headspace issue or the action is one which allows some stretch, cases don't lengthen from firing. Cases do lengthen from resizing and the amount of lengthening is related to the amount of sizing (chamber vs die dimensions). A sharp shoulder and a die which minimizes the amount of diameter reduction will reduce the amount of lengthening from sizing. I have done quite a bit of experimentation on this and the results are usually pretty predictable.
A 30/06 I tested lengthened the brass by .003" after thirteen shots (same case, no sizing) using 57 grains of 4350 behind a 180. The same rifle lengthened about .0005or so, per firing, if the case was neck sized only and about .004" if FL sized, without setting the shoulder back.
A Lee Enfield is a little stretchy. Loading the same case over and over with no sizing produced head separation after five or six shots. After rechambering to the Epps, I must have gotten a very slick surface in the chamber because the case didn't separate but the shoulder moved forward with each firing until I could no longer close the bolt. By the way, the Lee Enfield stretch allows the bolt to be closed even when there is over .010 of negative clearance. Try that with a Remington 700! WH

^^^^^^^^