I am now somewhat obsessed with having backups of backups of stuff but I am hoping to get some feedback/input from the collective group here. Eventually I am going to have a spare entire BCG for each rifle. One down, one on the way, and one to go on that, but I am thinking about more granular or other parts as well.

My main question is this: On an AR (doesn't matter if it's 5.56/300BLK or even bigger calibers) which components have you personally broken and or witnessed being broken (or just flat out worn out)?

I basically want to compile a list of the most commonly broken/worn out parts and start collecting an 'oops kit' of my own making with pins and rings and whatever other doodad I might need.

It can be anything. Have you ever worn out a trigger? Broken a firing pin? Broken an extractor? Or anything else not listed please make notes below.

I want this to be real world so I am looking for actual experiences or witnesses instead of just a generic recommendation of a kit that I might not ever use.