side of the aircraft, along with a Mk 8 sight. The launchers fired in pairs, one from each side to prevent the aircraft from becoming off balance. M3 systems were attached to the helicopter using Bell designed stores racks. The only difference between the XM3 and XM3E1 was that the launch tubes on the E1 were 4" longer. The XM3E1 was standardized as the M3. A subvariant of the M3 system was developed in 1964 by the US Army Limited War Laboratory that allowed equipped helicopters to produce a protective smoke screen. Called the "Troop Landing Smoke Screen" (TLSS), the system used modified M3 launch racks to dispense M8 smoke grenades. This system was later tested using M6 and M7 riot control grenades. XM5/M5 The XM5/M5 system consists of a nose turret for a single 40mm M75 grenade launcher. The mount was fully flexible and controlled by the pilot via a hand controlled sight electronically linked to the turret. The system either provided 150 or 302 rounds of ammunition. This system was also part of the armament kit for the ACH-47A. M6 Series The M6 system was one of the first systems to make use of the XM156/M156 universal mount, providing two M60C 7.62×51mm machine guns on either side of the helicopter. This system would later be expanded upon, but initially gave the UH-1 increased firepower and an improved offensive system over the skid mounts originally used. The various development stages of the M6 system mainly had to do with the "station" to which the M156 mount was attached. The position of the XM6 is not stated, but the XM6E2 was fitted to "station 69" (likely forward of the main cabin) and the XM6E3 was fitted to "station 136." Since the XM6E3 was standardized as the M6, "station 136" is assumed to be the aft of main cabin position that would become standard for M156 based systems. Some M6 systems were coupled the four guns with four MA-2/A 2.75" 2-Tube rocket launchers on each side of the aircraft, giving an even greater punch. This arrangement was later supplanted by the XM16/M16 system. XM9 A variant of the XM6/M6 system, the XM9 substitutes the four M60C 7.62×51mm machine guns with two M75 grenade launchers, one on either side of the aircraft. XM11, XM22/M22, and the Maxwell System Both of these armament systems were designed to allow the UH-1 to fire the