I loaned a National Match M1a to a fellow target shooter for about a year. I found he never cleaned his rifles, thought it was un necessary, when I got the rifle back, the gas mechanism was filthy and there were light rust spots on the external metal surfaces. If he had if for longer, there would have been rust pits in the metal, and probably the gas pistol. I saw one M14, a State Association rifle, the user had been loaned the rifle and told that it was un necessary to clean the gas system. His rifle was malfunctioning at Camp Perry. He came into my hut with the thing. It took almost all my strength to get that gas cylinder lock screw off, and then the gas piston was completely full of powder residue, and the gas piston had deep, I am talking swiss cheese sized rust pits. I had the tools to clean out the gas pistol, could do nothing about the pits, and told the guy that he needed to periodically clean the gas system. His rifle worked fine for the rest of NRA Highpower.
Even among experienced shooters, a lot of them are lazy, don't clean their guns, don't maintain their guns until something breaks or malfunctions, and, have gonzo ideas about load limits. Some will fire off loads above proof pressure and think that since the firearm has not exploded into fragments, then everything is OK.
If you want to see how people treat loaner equipment, go to Autozone and rent a tool. I recently went to Autozone and out of the three slide hammer pullers, I was able to cobble, from the parts of all three, one functioning slide hammer. Parts were missing, parts were smashed and dented, that is what fools do with loaner tools.
This was the axle:
And this was the bearing:
