They replace the broken or wore out pieces such as springs and parts on the bolt carrier groups.
They are returned to servicable condition and reissued.
So if the weapons are not able to be reissued by replacing small parts I would guess it gets destroyed.
My determination to not strike the first blow, but also to not stand mute and allow myself, and all that I believe in and stand for, to be trampled by men who would deprive me of my God-given, or natural right to suit my own end.