I have used them in 9mm, 44 and 45. I taper crimp, but even if you cut the plating with a roll crimp it will not cause a problem. In some guns, the rifling is enough to score through the plating, which is only paper-thin. I have found flecks of plating down range, which came off after the bullet left the barrel, but none that ever lodged inside the bore. Even if it did, it would be too small and thin to create a dangerous obstruction. It is still best to follow the manufacturer's guidelines on maximum velocities. The copper flaking seems mainly to occur with the heavier bullets at higher velocities.