Re: Resizing Belted Magnums
Just a thought on adjusting a FL die properly to just bump the case shoulder.
I often see suggestions to move the die in "small increments, like 1/4 of a turn, until you get it right." Friends, quarter turns of a sizer is a MASSIVE change to a case; it needs to be in MUCH SMALLER increments if it's to do you any good.
Consider that most SAAMI specs for bottle neck cartridges is around .008". A full turn of a 7/8x14 die moves it .0714", just over 71 thou. A quarter turn equals 17.85 thou, covering more than TWICE the normal allowable maximum range of headspace in just one adjustment! Adjusting your sizer in increments of 16th turn equals changes of 4.46 thou, or a bit over half the allowable headspace tolerance. That's certainly the largest amount of change you should make as you strive for proper fit to the chamber.
I put a series of prick-pin punch marks on the upper face of my sizer die lock rings, 16 of them, as evenly spaced as I can make them. I use those marks as a reference for die changes. I can easily make changes of half the distance between the marks. That's not absolutely precise but it works fine in practice.
The same sizing process IS valid for belted and rimmed cases as well.
Simply do your resizing work off the shoulder for all bottle neck cases and you can prevent a LOT of "normal" brass stretching that presents the danger of early head seperations.
Last edited by boomtube; 08-09-2009 at 04:41 PM.