Re: M1A ACCURACY EXPECTATION?
If you really read the 1960s-era match tuning works, you will find that about half of the NM mods and specs are for reliability.
The accuracy mods are bedding, unitizing, and clocking/shimming the gas cylinder...and most importantly, the barrel itself.
Op rod bending, spring guide, gas piston and cylinder dimension specs, tightening the op rod guide to the barrel, and the free opening and closing of the op rod/bolt system at 45 degrees or whatever or less tilt, those are all reliability mods. Every M1A or Garand I ever worked on would open and close completely, dry of all lube, at about 30 degrees tilt.
Considered accuracy but they give their benefit from making sight indexing more precise and repeatable: tightening up the barrel and splines with everything else that goes on it, tightening up the aperture to windage base fit, the two versions of NM windage, and the hooded aperture or smaller and slightly oversized-rack non-hooded NM aperure.
I have no experience with the shorter barrel M1As, but what I'm hearing is opposite of what the benchresters and boltgunners find about shorter barrels being on average more accurate. Stiffer and less barrel whip is the operative theory.