When roller lock rifles are put together wrong it can be a real pain! I fought a Century CETME for 4-5 years. New bolt head, carrier, rollers, furniture, sent back 3 times, got a new rifles on the last warranty repair. Things to look for: The rails should be squared not rounded. Trunnion should be welded in properly. Dimples in rear and front of receiver. Receiver widening from bolt head bumping the front of the trunnion causing rollers to try and set early. The PTR feels like they are built better to me. The Century stamped CETME was not the correct steel. They wouldn't even take a stanag scope mount.