M4 autocannon

37 mm Automatic Gun, M4
37 mm Automatic Gun, M4
Type	Autocannon
Place of origin	United States
Service history
In service	1942–1945
Used by	United States; Soviet Union
Wars	World War II
Production history
Designer	John Browning
Designed	1921–1938
Manufacturer	Colt
Produced	1939
Variants	M9, M10
Specifications
Mass	213 lb (97 kg)
Length	89.5 in (2.27 m)
Shell	37×145mmR
Caliber	37 mm (1.46 in)
Action	recoil operation
Recoil	9+5⁄8in (245 mm)
Rate of fire	150 rpm
Muzzle velocity	2,000 ft/s (610 m/s)
Feed system	30-round magazine

The37 mm Automatic Gun, M4,known as theT9during development, was a 37 mm (1.46 in) recoil-operatedautocannondesigned byBrowning Arms Companyand entered service in 1942.^[1]The M4 and its variants would primarily be manufactured byColt's Manufacturing CompanyandOldsmobile(under-contract by Colt) and is therefore sometimes referred to as the "Colt M4" or "Oldsmobile M4."^[2]It was primarily mounted in theBell P-39 AiracobraandP-63 Kingcobra,with theU.S. Navyalso utilizing it on manyPT boats.

Design

Designed primarily as an anti-aircraft weapon, the gun had amuzzle velocityof 2,000 ft/s (610 m/s) and acyclic rateof 150 rounds per minute. It was normally loaded with high-explosive shells, but could also be loaded with the M80 armor-piercing shell, which could penetrate 1 inch (25 mm) ofarmor plateat 500 yd (460 m). It was magazine-fed and could be fired manually or by remote control through asolenoidmounted on the rear of the gun.

Recoiland counter-recoil were controlledhydraulicallyby means of a piston and spring combination connected to the recoiling mechanism and operating in an oil-filled recuperator cylinder mounted to the stationary trunnion block assembly. The recoiling mechanism of the gun included the tube and tube extension, recuperator piston and piston rod, lock frame assembly, driving spring assemblies, and thebreechblockassembly. The nonrecoiling parts included the trunnion block group, the feed box and feeding mechanism, the recuperator cylinder and bushing, the back plate group, and the manual charger assembly.

Feeding mechanism

As the gun was originally designed,ammunitioncould be fed by a 5-round clip, a 15-round link belt, or a non-disintegrating 30-round endless belt magazine. The 30-round endless belt version was used exclusively in production. The M4 gun fed only from the left.

The 30-round endless belt magazine was given the designation M6; it had an oval-shaped framework (nicknamed a "horsecollar magazine" from its shape) providing a track for the endless belt.^[3]^[4]^[5]

Firing cycle

Initial loading and cocking of the gun were accomplished manually. A safety feature incorporated in the design of thetrigger mechanismprevented firing the round until the breech-block assembly was in the battery position.

The breech was locked and unlocked by recoil action which brings the operating level guide pins against cams to raise and lower the breechblock. The function of the breechblock was to assist in the final chambering of the round, close the breech, and actuate the trigger trip. It also provided a mounting for the firing pin.

The lock frame was retracted by recoil action during automatic firing and is forced forward by the driving springs. The major function of the lock frame assembly was to force the cartridge into the chamber, actuate the breech block, fire the round by means of the hammer striking the firing pin, extract the cartridge case from the chamber, and operate the ejector.

The back plate assembly, by absorbing the energy of the lock frame, reduced the shock against the carrier pin as the lock frame was hatched to the rear.

The driving spring assemblies held the lock frame against the carrier dog until the carrier was released by carrier catch which was pivoted by the incoming round. The springs then drove the lock frame assembly forward to operate the ejector, chamber the round and raise the breech block.

Initial extraction occurred during recoil. Extraction, ejection, feeding and loading were accomplished during counter-recoil. If the trigger was held in the firing position, the gun would continue to fire automatically until the magazine was empty.

US Army Air Forces

The 37 mm cannon was disliked by pilots for its low muzzle velocity, resulting in more pronounced drop than other contemporary weapons.^{[citation needed]}

The only standard aircraft armed with the M4 to see service were theBell P-39 Airacobraand the derivativeP-63 Kingcobra.It was used as a limited standard aircraft inNorth Africa campaignand the Pacific theater by the USAAF and Allied air forces.

Some YP-38s, the prototype model of theLockheed P-38 Lightning,mounted a single M4 before the armament scheme was finalized.^[6]Production Lightning models would replace the M4 with theAN/M2 20 mmcannon.

The experimentalXP-58 "Chain Lightning"was a larger, more heavily armed version of the P-38 Lightning equipped with quadruple M4 cannons instead of.50 caliberM2 Browningheavy machine guns in its nose. Its original purpose (like the GermanMesserschmitt Bf 110) was to destroy formations of bombers, but it was later re-envisioned as a ground-attack plane. The more pronounced ballistic trajectory was unfamiliar for American pilots, and the four M4s were replaced with a single75mm M5 cannonand a pair of.50 caliber heavy machine guns.

The first US jet, theBell P-59 Airacomet,saw two out of three YP-59s and the single XP-59 armed with twin nose-mountedM10 autocannons,a slightly updated and refined version of the M4. Production-model P-59s mounted a single M10 cannon in the nose bearing 45 shells, along with three M2.50 caliber machine guns bearing 200 rounds each.

US Navy

The M4 37 mm (1.46 in) automatic cannon was mounted on numerousU.S. Navy PT boatsas deck guns, beginning with theSolomon Islands campaign.Primary targets were the landing barges being used to move supplies down the island chain at night. At first, they were cannibalized from crashed P-39s at Henderson Field, and due to their success as an anti-barge weapon were used for the rest of the war. The M4s were initially mounted on a simple pedestal mount (often built at the front lines) with the standard horseshoe endless-belt feed being used. Later, an improved pedestal mount was designed for original equipment mountings on the boats. Handgrips of several configurations were used with various sights being tried. Most PT boat gunners used tracers to sight the fall of their shot. Beginning in 1944, the M9 model 37 mm (1.46 in) cannon was installed at the builders' boatyard as standard equipment.

Soviet Air Forces

During World War II the United States supplied theSoviet Air Forceswith the M4-equipped P-39 Airacobra and P-63 King Cobra. The U.S did not supply M80 armor-piercing rounds for theseLend-Leaseaircraft—instead, the Soviets received 1,232,991 M54 high-explosive rounds. The M4 was sometimes employed against soft ground targets on theEastern Frontbut was primarily used in air-to-air combat, in which role it was highly effective. The Soviets did not use the P-39 for tank-busting.^[7]Soviet pilots appreciated the M4's reliability but complained of its low rate of fire (three rounds per second) and small magazine size (30 rounds).^[8]

US-built contemporaries and successors

The37 mm M9 autocannonwas a derivative of the37 mm M1A2flak gun and used the longer, more powerful 37×223mmSR cartridge. Compared to the M4, the M9 had 50% more muzzle velocity (3,000 fps) from a 78-inch barrel (vs. 65-inch in M4), and was twice as heavy (120 vs. 55 pounds for the barrel alone); the whole M9 weighed 405 pounds vs. 213 of the M4. The cyclic rate was the same.^[9]Little is known about this gun's deployment; the only confirmed use is in the US Navy PT boats mentioned above.^[10]
The37 mm M10 autocannonwas a minor improvement of the M4. It was fed by metallic disintegrating link belt and had a slightly higher rate of fire at around 165 rpm.^[9]The M10 replaced the M4 in aircraft starting with the A-9 model of theBell P-63 Kingcobra.^[10]The disintegrating link belt made it possible to increase ammunition storage in theBell P-63 Kingcobrafrom 30 rounds to 58 rounds. TheBell P-59 Airacometalso mounted M10s; Two of three YP-59s and the XP-59 mounted twin nose-mounted M10s, with production models retaining only one.

Notes

^Bishop, Chris (2002).The Encyclopedia of Weapons of World War II.New York: Friedman/Fairfax Publishers. p. 161.ISBN 1-58663-762-2.
^"Oldsmobile, Lansing, Shells, Cannons, and World War Two – Military History of the Upper Great Lakes".
^Emmanuel Gustin; Anthony G. Williams (2003).Flying Guns: The Development of Aircraft Guns, Ammunition and Installations, 1933-45.Airlife. p. 153.ISBN 978-1-84037-227-4.
^Ian V. Hogg (2001).The American Arsenal: The World War II Official Standard Ordnance Catalog of Small Arms, Tanks, Armored Cars, Artillery, Antiaircraft Guns, Ammunition, Grenades, Mines, Etc.Greenhill Books. p.217.ISBN 978-1-85367-470-9.
^Gordon Rottman (2011).US Patrol Torpedo Boats: World War II.Osprey Publishing. p. 22.ISBN 978-1-78096-208-5.
^Caidin, Martin (2001)."YP-38 37mm".Fork-Tailed Devil: The P-38.USA: J. Boylston, Publishers.ISBN 9780743413183.Archivedfrom the original on 30 November 2021.Retrieved30 November2021.…one 37mm cannon…
^Loza, Dmitriĭ Fedorovich (2002).Attack of the Airacobras: Soviet Aces, American P-39's and the Air War against Germany.University Press of Kansas. p. 359.ISBN 0-7006-1140-1.
^Drabkin, Artem.The Red Air Force at War: Barbarossa and the Retreat to Moscow – Recollections of Fighter Pilots on the Eastern Front.Barnsley, South Yorkshire, UK: Pen & Sword Military, 2007, p. 133.ISBN 1-84415-563-3.
^^a ^bGeorge Chinn1951, The Machine Gun: Development During World War II and Korean Conflict by the United States and their Allies of Full Automatic Machine Gun Systems and High Rate of Fire Power Driven Cannon, Volume III, Parts VIII and IX., p. 352
^^a ^bAnthony G. Williams (2002).Rapid Fire: The Development of Automatic Cannon, Heavy Machine-Guns and Their Ammunition for Armies, Navies and Air Forces.Airlife. pp. 155–156.ISBN 978-1-84037-435-3.

References

War Department,U.S. Army Coast Artillery Corps,Training Manual TM-9-2300Standard Artillery and Fire Control Materiel(7 February 1944)
War Department, Training Manual TM 9-24037-mm Aircraft Gun Materiel M4(30 March 1942)
War Department, Training Manual TM 9-124037-mm Automatic Gun M4 (Anti-aircraft)(3 January 1942)
War Department,US Army Ordnance Corps,Standard Nomenclature List Catalog, Group A, Subgroup A46ORD SNL A-46 (37mm Gun, Automatic, models M4 & M10)
P-63 KingCobra - Browning M4 37mm Auto Cannon Gun
United States of America 7 mm/56 (1.46 ") M4

External links

Media related toM4 cannonat Wikimedia Commons

[1] Bishop, Chris (2002).The Encyclopedia of Weapons of World War II.New York: Friedman/Fairfax Publishers. p. 161.ISBN 1-58663-762-2.

[2] "Oldsmobile, Lansing, Shells, Cannons, and World War Two – Military History of the Upper Great Lakes".

[GustinWilliams2003-3] Emmanuel Gustin; Anthony G. Williams (2003).Flying Guns: The Development of Aircraft Guns, Ammunition and Installations, 1933-45.Airlife. p. 153.ISBN 978-1-84037-227-4.

[Hogg2001-4] Ian V. Hogg (2001).The American Arsenal: The World War II Official Standard Ordnance Catalog of Small Arms, Tanks, Armored Cars, Artillery, Antiaircraft Guns, Ammunition, Grenades, Mines, Etc.Greenhill Books. p.217.ISBN 978-1-85367-470-9.

[Rottman2011-5] Gordon Rottman (2011).US Patrol Torpedo Boats: World War II.Osprey Publishing. p. 22.ISBN 978-1-78096-208-5.

[Caidin_2021-11-30-6] Caidin, Martin (2001)."YP-38 37mm".Fork-Tailed Devil: The P-38.USA: J. Boylston, Publishers.ISBN 9780743413183.Archivedfrom the original on 30 November 2021.Retrieved30 November2021.…one 37mm cannon…

[7] Loza, Dmitriĭ Fedorovich (2002).Attack of the Airacobras: Soviet Aces, American P-39's and the Air War against Germany.University Press of Kansas. p. 359.ISBN 0-7006-1140-1.

[8] Drabkin, Artem.The Red Air Force at War: Barbarossa and the Retreat to Moscow – Recollections of Fighter Pilots on the Eastern Front.Barnsley, South Yorkshire, UK: Pen & Sword Military, 2007, p. 133.ISBN 1-84415-563-3.

[Chinn-v3-9] George Chinn1951, The Machine Gun: Development During World War II and Korean Conflict by the United States and their Allies of Full Automatic Machine Gun Systems and High Rate of Fire Power Driven Cannon, Volume III, Parts VIII and IX., p. 352

[Williams2002-10] Anthony G. Williams (2002).Rapid Fire: The Development of Automatic Cannon, Heavy Machine-Guns and Their Ammunition for Armies, Navies and Air Forces.Airlife. pp. 155–156.ISBN 978-1-84037-435-3.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]