Something else no one ever wants to talk about is the 5.56 ammo itself. When Armalite (Gene Stoner) designed the system, the powder used was IMR type. The Army went to Ball powder AND THEN THE PROBLEMS STARTED. It’s my impression they are still using ball powder today.
I picked up a POF-USA 415 (gas piston system) a couple of years ago. I can be a bit more abusive to it than my Colt H-Bar. You really notice the difference when you pull the bolt to clean it. Since it’s not eating and s*itting in the same place, there is a whole lot less carbon and crap to get out.
Even Eugene Stoner realized the flaw in the AR-15... which is why he went on to design the AR-18.
He tried to get the government to adopt that rifle instead, but they’d already settled on the -15 and weren’t interested.