George, Don't know if this is what you refered to but Japan made M12's have the equivalent of a trigger disconnect to prevent slam firing. With the Japanese guns, if you shoot, and leave your finger depressing the trigger, shuck and try to shoot again without removing your finger from the trigger, it won't fire. You must release trigger between shots. Same with older M37s versus new M37s. My old M12s and M37s can shoot as fast as I can pump if I leave the trigger depressed. Gil