"C7's" did not have an optical sight, it had the old style A1 type reciever, the barrel was heavy, light heavy and the flash hider had no slots on the bottom. You will not be able to install a front sight assembly with a bayonet lug on that barrel because the cross pins will not line up. The front sight assemblies are fitted to the barrel then the holes are drilled for the taper pins. "C7A1" had flat top recievers and optical sights and I tgink the C7A2 now have the carbine stocks fitted. Might be wrong about that.
Scott