I recently aquired one of these to tinker with. Yes I know nobody likes them but its something to do. It has a broken bolt. I called Bushmaster and they said it would require a new barrel and bolt. The original bolt has a different head then a regular AR bolt. Otherwise its the same. Instead of being squared off teeth they are rounded. I stuck in a bolt out of one of my other rifles and it slides in and out of the lugs fine, it twists right into the lugs like its supposed to. I'm wondering what would happen if I tried to fire it like this. Or should I just break down and buy a new barrel and bolt? Or maybe just a barrel extension and a new bolt? I'd like to keep the barrel on it, its stainless and fluted with a nice detatchable muzzle break on it.