First of all, you don't want maximum level, bolt gun appropriate loads, in your M1a. You put too much pressure down the gas system, you will have failures to extract, and possible bolt over rides. And it will be hard on the rifle.
In my opinion, life is some much better with an M1a pushing a 150 grain bullet at 2700 fps than at 2800 fps. This load, though it is not Varget, is just about perfect for an M1a.
M1a, Douglas Barrel
150 gr Hornady FMJBT 43.5 grs AA2520 wtd Lot 9595 Czech Mixed LC WLR OAL 2.785
18 May 2008 T = 70 °F
Ave Vel = 2700
Std Dev = 30
ES = 85
High = 2736
Low = 2651
N = 10
I examined my 168 Match data, I think a load around 44.0 grains Varget will be close to a maximum load with a 150. My experience with Varget was that it was a bit slow for a M1a, I experienced case head separations, which is an indication the powder is too slow for the gas system in that rifle. I do know of others who have used Varget, so, maybe Varget is on the edge of being marginal in M1a's. It is a great bolt gun powder. I really recommend the 4895 powders in the M1a. That is, IMR 4895, H4895, or AA2495. The US Army developed the T65 cartridge with IMR 4895, and all the National Match ammunition was loaded with IMR 4895. I am of the opinion that this powder should be the first choice, and then, try IMR 3031, which is a bit faster. The slowest I would go is IMR 4064. And, keep this in mind again, you are loading for function and reliability, not speed in this rifle. Leave the hot rodding to bolt guns.