Aloha CarryAGlock:
Man, I feel like I know ya... It's funny to see you and HG112 show up in the same thread... looks like we all like M1A's and the same kind of scopes... lol.
I am new to this board, so if I am out of line, please let me know...
I think TEA is getting you off in the right direction... in getting your rifle "Match" ready. The M1A is a peculiar type of animal (IMHO) and much different from the AR's, FAL's, etc. It requires a good barrel and all of the barrel attached components to be working together, tight and in proper alignment... so a good barrel, NM flash hider or NM reaming, NM gas cylinder, NM op rod guide, NM op rod spring guide and your bedding at the proper angle to achieve that "correct" amount of tension on the front band, will get you shooting them good groups...
To help and aid you in shooting better, a trigger job, and NM sights will do the trick...
To validate your work and your shooting, a scope will help... A Brookfield (v. expensive), a Smith or an ARMS will serve you well... the Leupold is just "GOOD" glass... but you might consider the M1 turrets if you are shooting for groups. The M3 turrets are more for shooting "man size" targets and correct bullet drop compensation.
Right now, as you described your M1A, it sounds like you are getting decent groups as is... but to chase the elusive sub or 1 MOA, it will take some work.
Why did your AR perform 1 MOA? Maybe you got a super good one! It would be my guess... I don't know... but you can make your standard M1A shoot better than it is doing if you really want it to...
I am not sure if any of the "standard" grade battle rifles shoot 1 MOA or better. My FAL certainly won't and I know the HK91 doesn't...
In any case, Good Luck in your pursuit of the 1 MOA, I have a M1A Loaded rifle that I too am working on to do the same thing...
Aloha and Best Wishes,
Tom O.