in favor of the M55. During the Korean War, the M55 and M16 saw extensive combat, and lessons learned in Korea led to the conversion of an additional 1200 M3 halftracks into the M16A1 variant by adding an M45 turret. These can be identified by the lack of fold-down armor and rear troop door on the crew compartment and were often fitted with the roller front bumper instead of the winch bumper fitted to all M16s. In 1954 an additional modification was made to roughly 700 M16 MGMCs, adding the rear troop door and bolting the fold-down armor in the up position. This modification became known as the M16A2 MGMC. The M55 received a new, more powerful generator in the 1960s and served through the Vietnam War, usually mounted in the back of an M35 2.5 ton or M54 5-ton gun trucks. Operation The M45 is operated by two loaders and one gunner. The mount is capable of traversing a full 360 degrees around, with an angle elevation between -10 and +90 degrees. Traverse and elevation are electrically driven, powered by two rechargeable 6-volt batteries. All four guns could be fired at once, but standard practice was to alternate between firing the upper and lower pair of guns, allowing one pair to cool while the other was in use. This allowed for longer periods of action as overheating of the gun barrels was lessened. The "tombstone" model M2 ammunition chests held 200 rounds each—with one ammunition chest on an M45 system holding ten times as many rounds as each of the four twenty-round 20mm magazines of the German Flakvierling system held (and which, on the German ordnance system, had to be changed every six seconds on each gun of the quartet to ensure its own top 800 rpm "combined" firing rate), with each M2 ammo chest weighing 89 pounds each when full. Gallery Operators See also List of U.S. military vehicles by supply catalog designation DTM-4 Flakvierling 38, quadruple 20 mm autocannon-based weapon system mountable onto a Sd.Kfz. 7/1 half-track, as just one example Wirbelwind, quad-barrel 2 cm Flakvierling 38. ZPU-4, quadruple 14.5mm heavy machine gun-based weapon system mountable onto technicals, cargo trucks, and APCs. Notes References Training Manuals TM 9-2800 Military vehicles TM 9-2010 TM 9-1223 FM 44-57 M20 trailer SNL G220 TM 9-789 M17 trailer SNL G221 TM 9-881 External links Scribd's Archived M45 Quadmount Manual M45 Quadmount