Keep this in perspective before dumping BIG $$$ into your 14.
I've seen several Norinco M14 rifles with all stock parts, that would shoot 1" - 1 1/2" with their favorite commercial ammo. With some of these, simply fitting in a GI bolt, a proper tightening and a decent trigger job, has turned basically stock Chinese M14 rifles into SUB-MOA shooters. Reloading may improve accuracy even more.
The M14 type rifles are incredibly sensitive to variations in ammunition. Test groups have ranged from sub MOA to 4" with the same gun, with no other change than ammunition. Finding the ammunition your individual rifle prefers is one of the easiest and most effective "accurising" tricks available for the M14.
If you want to spend BIG $$$ on accurising an M14, be aware that many "accurising" tricks and tweaks used on the M14 subtract only fractions of an inch from a group, and added all together [ at a cost of perhaps THOUSANDS of dollars in parts and labor ] they can make an M14 almost as accurate as an off the shelf, cheap, ho hum, bolt action rifle.
Does this suggest the point of diminishing returns?
Basic Norc with a bit of DIY labor - $ 500 shoots approximately 1 1/2"
add a GI bolt - $ 800 - if you get lucky, the 14 may now shoot sub-MOA
TOTAL Full house M14 - SEVERAL THOUSANDS of dollars, may shoot better, may NOT!!
But for those of you who want to chase the elusive holy grail of more accuracy from an M14 Money Pit,
good luck to you!!
as usual,
YPMMV
LAZ 1