Sometimes after cleaning a rifle barrel I'll put 2 of em into the breach and fire em off. When I do this the rifle seems to sound and feel exactly the same as when I shoot a pellet. I know that's not very scientific but it's the only way I can describe it. I don't use them every time I clean a barrel, far from it, but every once in a while I will use them. I haven't noticed any problems with my rifles as a result.
I"m sure someone with a lot more knowledge than me will chime in and give a definitive scientific answer,,,, then we'll all know.......
Jeff