Yes the US factory ammo (I had experience with the Winchester 8x57 ammo) is very underloaded for the run of the mill 0.323 8mm rifles. I think they do this to avoid getting sued if someone uses it in a poor condition rifle in 0.318 and blows it up. They use 0.321" projectiles too (surprised they don't use 0.318"). My rifles didn't shoot this stuff well and the primers backed out (ie very light load).