Trigger slap is a phenomenon present on a number of gun designs, but most commonly encountered on semi-automatic AK-47, AK-74 and MAC-10 clones. In some of these guns the trigger “slaps” against the operators trigger when it resets. It can range from a mild annoyance to bad enough to numb or hurt the operators finger. In the case of MAC-10 clones, it is the result of the BATFE rules requiring them to fire from a closed bolt. This design problem was not as much of a issue with the original open bolt MAC-10 machine pistols.
Masterpiece Arms has developed a hammer/disconnect that completely eliminates trigger slap. It will be installed on all their MAC-style guns starting in January next year. They will also be selling it separately for $39.99. It woks with both MPA’s own guns as well as MAC style guns manufactured by Cobray/Leinad.