The MAC-10 (or Military Armament Corporation Model 10, officially the M-10) is a highly-compact, blowback-operated submachine pistol developed by Gordon B. Ingram in 1964. The MAC-10 is similar in design to the Israeli Uzi submachine gun, with the ammunition magazine built directly into the handle. This feature allows for quick reloading in the dark. The main difference between the MAC-10 and the Uzi is that the MAC-10 is chambered for the powerful .45 ACP cartridge while the Uzi is only chambered in 9mm. The MAC-10 is also of a much cruder and simpler design than that of the Uzi, which allows for fast production.
The MAC-10 was carried by the henchman who told Targo about the piece of scrap metal on the container that was supposed to be gold bullions they stole in the Federal Reserve Bank. After proving Targo about it in the cargo hold, McClane arrives and kills him after saying in German, "Don't Shoot.". After the grueling battle with Targo, McClane incapacitates him and takes the MAC-10 gun from the dead henchman and proceed above the ship.
He proceed to the bridge while carrying the MAC-10 with him. When he sees no one there, he checks on the radio to the Coast Guard about the ship. As the ship was tracing the signal, McClane sees the real 2400 pounds of liquid explosives on the ship and realized that the bomb in the school was not real. Then Simon Gruber and his men surrounded McClane and takes the MAC-10 and his Beretta 92FS pistol away from him.