I really do know what their tolorance is taking the 50 cal which is what we see the most of all the ones I have had reason to check have been between .500 and .501 I consider that as in the proper range for a 50 cal. the one thing many people have had to deal with in the last few years that I think is uncalled for is burrs on the edge of the rifling , not to hard to deal with if you know how but uncalled for. Lee