I'm tuning a M14 with scope and good trigger. I've been working 42 gr of RL 15 on a 165 Sierra Game King. I shot some Federal 175 Sierra Matchkings in it and they weren't bad. Standard rifle, 22 in bbl syn stock. Any loads on any of powders above and I have other projectiles from 125 gr Nosler Bt tip to 150 grain

http://www.zediker.com/downloads/m14.html
Good reading if you have not already. Note the caution about using Varget and slow powders in the M14 type of rifles.
I use AA2495. I have to rework my load since I recently had to get a new canister. I had used 43.2 grains AA2495 with the 168 gr. SMK.

I'd lean to the faster burning powder of 4064 in the M1A rifles. If you run a slower powder like R15 or Varget, I wouldn't run a max load.

I use 4064 with 175's and IMR4895 with 165/168's. Have used 43.1 RL15 with 175's before (M118LR clone) in other rifles with great results....wouldn't hesitate to use it in my m14s.