I have a M-16.bought a 9mm upper for it.and did some reverse enginering and made an adapter for the mag well to accomidate colt 9mm mags.seems the hammer on the lower is not really made to operate the bolt on the upper.the bolt where the hammer is brought back is sharp and is nicking the hammer face and I don't believe the hammer on a lower 9mm is the same as a hammer on the lower 5.56.any one know about this?colt will not talk to me about machine guns.and from what I hear will not talk with any one over the phone about thier machine guns.