[Arsenal]

When you remove the barrel, make sure not to lose the detents, unless you like cleaning paint out of lots of tiny linkages and such.

Every once in a while you should check that all of the pivot pins in the trigger linkages are secure. As far as I can tell, they're pressed in, and I had one pop out during a game once. I've never heard of anyone else having the same problem, though, so it may have been a fluke.

Otherwise, it's basically bulletproof. Shoot, my brother ejected a charged mag onto a concrete floor from 4 feet up. There's now a fleck of paint missing from the mag, and there's a chip in my garage floor. The mag still works perfectly; these things are tough.