GP-11 ammo.
Its as good as any match grade ammo made.
My handloads shoot about as good as the GP-11, just with a lot less recoil.
The GP-11 bullets have a boat tail on them, are profiled similar to a VLD bullet and have a diameter of .3075"
The K-31 bore dimensions are a bit smaller (0.296-0.297 x 0.3075) than a standard 30 caliber (0.300x0.308 surplus springfields tend to run closer to 0.310") part of the reason why its harder to do better with handloads may be becauseof the dimensions of standard .308 bullets- that's just my theory though.