Re: How do I get oal and headspace on an M1A?
The proper method to set up headspace from the M1A/M14/M21 uses the rifle itself as the headspace guage. The method is to disassemble the bolt, then reassemble the barreled action only, without the recoil spring or spring guide. Lube normally.
Using a cartridge that has been fired and will not chamber because of excessive shoulder length, resize it to
shorter lengths in small increments.
When the rifle can be tilted with the muzzle 30degrees down and the bolt and oprod will slide and lock with the oprod at full forward stroke from gravity alone with the case in the chamber, headspace is correct. If you can still push the oprod further forward by hand, the case still needs to be shorter in the shoulder.
As far as seating depth and OAL are concerned, seating to magfeed length is good enough that seating longer doesn't buy enough accuracy to offset the hassle of single feeding. For matches, feeding methods are specified, and for slow fire, where single feeding is mandated, extended seating lengths are justified.
Greg
