Ovidio, the hot gas going into gas cylinder to work the action erodes the metal if you don't clean it properly and often. Even had carbon tubes around the holes in the gas cylinder. Armourer called it flame cutting, so I do too. Might also be because the rifle was shot too hot to hold onto with gloves on.
After about 5 000 shots and not cleaning properly might have been the cause of the gas cylinder having to be replaced, but it was my competition gun and I just kept on shooting. We're talking couple hundred rounds a day if I could get away.