Someone over on Reddit posted about this range rental AR-15 that went kaboom after 100,000 rounds. Good thing no one was hurt.
Back story: I work at a SoCal indoor shooting range and this was ‘Maggie’ our house-built AR (so cleverly named for the furniture, har har). This poor thing was rode hard and put away dirty more often than not for approximately 3 years of 7-days-a-week operation. Our best estimate on the low end is that it has seen about 100,000 rounds in its lifetime (probably much more, with a minimum of 1,000 rounds-a-day going through it). Rebarreled, replacement gas systems, springs, bolts, etc as needed. She finally gave up the ghost in the most epic way possible, literally coming apart in a customer’s hands after finishing a magazine. No one got hurt, and it was all laughs today thankfully, but its just something you don’t see everyday. Failure point is the threaded portion of the upper receiver, nice clean break exposing the bolt face and barrel on the other side.
That wasn’t the rifle failing, that was the guy who rebarreled it cracked the reciever when they torqued the barrel nut. They should have used a reaction rod