|
Coop is probably right.
Of the three styles of sizing, partial sizing with FL dies is most likely to cause cases to "grow" a bit.
It's common sense, really. If you leave a tiny gap between the cartridge shoulder and the die, but squeezus the bejeezus out of the rest of the case, the brass wants to go into that gap. So the case "grows" a bit in length, taking the neck section right along with it. That's both the benefit AND the bane of partial sizing. It allows one to get a precise headspace setting for a particular chamber, but it also requires one to trim - at least once.
After the case is fireformed to that chamber, the stretching should be reduced or stopped for subsequent sizings. But there's also the expander ball drag. Either FL or partial sizing entails pulling the expander ball back through the neck as the final event in that loading step. Unless the inside of the neck has been cleaned of powder/primer residue, the expander ball really pulls hard to get through the neck. MOST case stretching happens right there.
Remedy? Clean and lube case neck ineriors or get a carbide expander ball or use a neck sizer of the collet or insert style that don't have expander balls.
Or just reload cases through two trimmings and then recycle them when they need the third trim. Most brass is cheap enough to make the "worries" go away. And you get money back at the recyclers!
|