I get 1.5MOA at 100 yards with Malaysian surplus from 1985 in my Century FAL.
I did have custom trigger and barrel work done, however.
Probably cost me an extra $400.
But here's the thing:
A. The FAL and the AR-10 (Which is no more accurate, from my experiences of 5+ models) are not sniper rifles.
B. An off the shelf M-14, even a custom job, is not a ready made sniper rifle. It is not anywhere near the accuracy of an M-21. The M-21 uses the same action, but the barrel and stock are totally different. The barrel is floated, for one, which is a night and day difference. They are not the same gun any more than than an M-24 the same as a Remington 700, which also share the same action.
If you want a long range accuracy gun, you buy a gun that is designed for long range accuracy. PROTIP: It will more likely than not be a bolt action rifle.
Having said that, 90+ percent of people can't hit at less than 3 minutes of angle anyway. Make sure you're that good before you waste the money on a gun that can do something that you can't.