37 Mm Gun M3 - Self-propelled Mounts

Self-propelled Mounts

Two tank gun variants were developed based on the barrel of the M3. The first, initially designated M3A1 but renamed M5 on 13 October 1939, was shortened by 5.1 in (130 mm) to avoid damage to the tube in wooded areas. Later, a variant with a semi-automatic breech (with empty cartridge ejection) was developed. This variant—initially designated M5E1, adopted as M6 on 14 November 1940—received a full length barrel. The tubes were interchangeable, but replacing M5 with M6 and vice versa would result in an unbalanced mount and was therefore prohibited. These guns were mounted on several models of tanks and other armored vehicles:

• Light Tank M2A4: M5 in mount M20. The recoil mechanism, protruding beyond the gun mask, had to be protected by an armored casing.
• Light Tank M3: M5 in mount M22, in late production vehicles M6 in mount M23. These mounts were fitted with more compact recoil mechanism, eliminating the need for the protective casing.
• Light Tank M3A1, M5: M6 in mount M23.
• Light Tank M3A3, M5A1: M6 in mount M44.
• Light Tank (Airborne) M22: M6 in mount M53.
• M3 series medium tanks (as a secondary weapon): M5 or M6 in mount M24.
• Heavy Tank M6 (as a secondary weapon): M6 in mount T49.
• LVT(A)-1 "amtank": M6 in mount M44.
• 37 mm Gun Motor Carriage T22 - eventually Light Armored Car M8: M6 in mount M23A1; the competing designs 37 mm Gun Motor Carriage T43 / Light Armored Car T21 and 37 mm Gun Motor Carriage T23 / Light Armored Car T23 mounted the same weapon.
• Armored Car T13.
• Armored Car T17: M6 in mount M24.
• Armored Car T17E1 in the "Staghound Mk I" configuration: M6 in mount M24A1.
• The first pilot of the Armored Car T18: M6. The production variant T18E2 received the 57mm M1.
• Armored Car T19: M6 in mount M23A1.
• Armored Car T27: M6 in mount M23A1 modified.
• Armored Car T28 / M38: M6 in mount M23A2.
• British Humber Armoured Car Mk IV: M6.

Versions of the gun in turret mounts were also used in the Medium Tank T5 Phase III (T3 barrel, mount T1), in the Medium Tank M2 / M2A1 (M3 barrel, M2A1: mount M19), and in the 37mm Gun Motor Carriage T42 (mount M22).

In addition, M3 on different pedestal mounts was mated to a number of other vehicles resulting in an assortment of 37 mm gun motor carriages. Only the M6 reached mass production.

• 37 mm Gun Motor Carriage T2 (Bantam jeep).
• 37 mm Gun Motor Carriage T8 (Ford 4x4 "Swamp Buggy").
• 37 mm Gun Motor Carriage T13, T14 (Willys 6x6 "Super Jeep").
• 37 mm Gun Motor Carriage T21 / M4 / M6 (Fargo 3/4 ton 4x4 truck).
• 37 mm Gun Motor Carriage T33 (Ford 3/4 ton 4x4 cargo carrier).
• M3A1E3 Scout Car.
• The gun was sometimes mounted on M2 Halftrack, M29 Weasel and on the 1/4 ton Willys MB / Ford GPW jeep (see photo on the right).

On several occasions, the M3 was mounted on PT boats to increase their firepower. One of these boats was John F. Kennedy's PT-109. The gun with its wheels removed was mounted on wooden planks nailed to the deck.