I bought a CMMG that was at a price i could not resist. All was fine until I tried to change front standard from sight to a gas block with rails. They have some sort of proprietary pin setup that kept the gas block from mounting up solid and it developed a leak causing FTE jams. The local shop had to order new sight pins from CMMG to get it put back in stock form. No more problems in stock form. I don't think there are any other parts that don't interchange. So; good rifle at an affordable price just don't mess with the stock gas setup on the front end.