The M13 and M16 MGMC (Machine Gun Motor Carriage) were the US's main machine gun-based anti-aircraft vehicles, all of which were based on the M3 half-track and armed with Browning machine guns in specialized mounts. The chassis of the M3 was broadly unchanged with the troop compartment replaced by a fighting compartment for the operation of one of two mounts which were installed on a turntable which allowed for full traverse. The first, which was used on the M13 and M14, was the Maxson M33 mount which featured twin 0.5-in M2 Browning machine guns. This was operated by a gunner sitting in the middle, protected by an armored shield and with an electrical generator behind him which gave the mount full powered elevation and traverse and also allowed it to be used when the vehicle's engine was turned off. It was soon realized that two machine guns were not enough, resulting in the Maxson M45 quad-mount. The resulting M16 finally provided anti-aircraft gunners with sufficient volume of fire to take down most aircraft. The M13 served briefly but the M16 soon became the US Army's main SPAAG along with the gun/cannon-armed M15. The M16 proved particularly useful for defending against strafing runs but once the risk of Luftwaffe attacks began to recede, began to be employed as a fire support weapon where its effectiveness against enemy infantry earned it the nicknames 'meat chopper' and 'Krautmower'. Perhaps the M16's most notable action was the defense of the Ludendorff Bridge in March 1945, where it fended off repeated German attacks even with jets. The M16 also saw further combat in Korea but gradually became obsolete in the jet age, although many were exported after the war in addition to the large numbers provided other Allies as part of Lend-Lease (where they were known as the M14 and M17 respectively).

Efforts to develop a SPAAG system began in 1940 with the first prototype known as the T1 which used a Bendix twin Browning aircraft turret mounted on a jeep or a truck. The T1E1 followed, using an H2 half-track before moving to the definitive Maxson M33 mount in the T1E2 while a Martin bomber turret was tested on the T1E3. The T1E4 replaced the M2 with the larger M3 and this entered production as the M13. Meanwhile, the quad-mount M45 was developed and tested on the T1E2, which entered production as the M16 on the M3 chassis as well. Many M13s were later converted to M16 standard and during the Korean War additional M3s were converted as well, these featured a large folding shield in front of the mount and were designated M16A1. Two very similar versions to the M13 and M16 were built for Lend-Lease using the very similar M5 half-track chassis. These were the M14 (with a twin M33 mount) and the M17 (with a quad M45 mount). Most were sent to Britain but subsequently re-converted to half-tracks.