I have a Windham Weaponry model R18FSFSM-308. Obviously with them going out of business parts support becomes an issue. My question is what parts if any are unique to Windham that would prevent using common AR parts if something breaks on down the road? It is a nice gun and I hate to think of getting rid of this if parts will be a problem on down the road. I read comments regarding this and the authors always seem to leave it at some parts are unique and never say exactly what. Keep it or sell it is another question.