Then you'd better not ever operate any type of firearm, as they all exhibit a great deal of metal-to-metal contact during their normal operation.

If metal-to-metal contact of so harmful, then firing the rifle would wear it out just as fast as cycling it by hand. If a semi-auto couldn't handle the repeated impact of the action cycling then the life expectancy of a semi-auto firearm would be very short. But the fact is that semi-auto firearms are capable of experiencing literally thousands of shots without appreciable wear, with the bolt slamming home at full force every time. The simple fact is that the yield strength of the metals used so far exceeds the forces applied to them during all normal operating conditions that no appreciable damage will ever occur from the simple manual manipulation of the slide/bolt.

Mike