anything from 50-80g should be ok to shoot. The ideal bullet is a 75 or 77 grainer IMO. They generally give excellent results in barrels with a 1/8 twist, and they do for me in my AR with the same twist. I haven't tried the 69 SMK, but I've heard good things about them in the reloading forum.
If you are rolling your own, try RE-15 or Varget behind heavier bullets. They are excellent powders and aren't temperature sensitive at all. Perfect for 75/77g bullets.