Re: M1A Super Match Accuracy
Generally, I'd expect a full-on, properly built NM M14 (or M1A) to shoot right around MOA, or just a bit less. When I was with 5th Army MTU, they tested their rifles in an accuracy cradle at 300 yards, and required right at 3" for ten-round strings with M118. The M852 (168 grain HPBT Match rounds, no longer being loaded or in service) or the new M118LR (175 HPBT) will improve that just a bit, so I'd be looking for somewhere around 2.5" or a bit better, ten-rounds at 300.
As has been mentioned, these guns don't shoot like this for very long unless they're properly maintained and rebuilt regularly. I'd agree completely with the comments about their needing to be re-bedded every 1,000 rounds or so just to stay in tune. This is one of the factors that have led to the M16s completely eclipsing the M14s in High Power competition today; they don't need this sort of constant attention. Build them right, and the next time it'll truly need to see an armorer is when the barrel is shot out and needs to be replaced. Not true with an M14. They need to be kept in tune by frequent visits to the armorer's shop, and will go through several bedding jobs long before the barrel gets shot out and needs a full rebuild.