The 37 mm Automatic Gun, M4, known as the T9 during development, was a 37 mm (1.46 in) recoil-operated
autocannon
An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber ( or more) armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bull ...
designed by
Browning Arms Company
Browning Arms Company (originally John Moses and Matthew Sandefur Browning Company) is an American marketer of firearms and fishing gear. The company was founded in Ogden, Utah, in 1878 by brothers John Moses Browning (1855–1926) and ...
. The weapon, which was built by
Colt
Colt(s) or COLT may refer to:
*Colt (horse), an intact (uncastrated) male horse under four years of age
People
* Colt (given name)
*Colt (surname)
Places
*Colt, Arkansas, United States
*Colt, Louisiana, an unincorporated community, United States ...
, entered service in 1942. It was primarily mounted in the
Bell P-39 Airacobra
The Bell P-39 Airacobra is a fighter produced by Bell Aircraft for the United States Army Air Forces during World War II. It was one of the principal American fighters in service when the United States entered combat. The P-39 was used by the ...
and
P-63 Kingcobra
The Bell P-63 Kingcobra is an American fighter aircraft that was developed by Bell Aircraft during World War II. Based on the preceding Bell P-39 Airacobra, the P-63's design incorporated suggestions from P-39 pilots and was superior to its pr ...
, with the
U.S. Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage of ...
also utilizing it on many
PT boats
A PT boat (short for patrol torpedo boat) was a motor torpedo boat used by the United States Navy in World War II. It was small, fast, and inexpensive to build, valued for its maneuverability and speed but hampered at the beginning of the wa ...
.
Design
![M4 cannon Keski-Suomen ilmailumuseo](https://upload.wikimedia.org/wikipedia/commons/6/69/M4_cannon_Keski-Suomen_ilmailumuseo.JPG)
Designed primarily as an anti-aircraft weapon, the gun had a
muzzle velocity
Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately to i ...
of and a
cyclic rate
Rate of fire is the frequency at which a specific weapon can fire or launch its projectiles. This can be influenced by several factors, including operator training level, mechanical limitations, ammunition availability, and weapon condition. In m ...
of 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) of
armor plate
Military vehicles are commonly armoured (or armored; see spelling differences) to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighting ...
at . It was magazine-fed and could be fired manually or by remote control through a
solenoid
upright=1.20, An illustration of a solenoid
upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines
A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...
mounted on the rear of the gun.
Recoil
Recoil (often called knockback, kickback or simply kick) is the rearward thrust generated when a gun is being discharged. In technical terms, the recoil is a result of conservation of momentum, as according to Newton's third law the force requ ...
and counter-recoil were controlled
hydraulic
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
ally by 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 the
breechblock
A breechblock (or breech block) is the part of the firearm action that closes the breech of a breech loading weapon (whether small arms or artillery) before or at the moment of firing. It seals the breech and contains the pressure generated by th ...
assembly. 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,
ammunition
Ammunition (informally ammo) is the material fired, scattered, dropped, or detonated from any weapon or weapon system. Ammunition is both expendable weapons (e.g., bombs, missiles, grenades, land mines) and the component parts of other weap ...
could 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.
Firing cycle
Initial loading and cocking of the gun were accomplished manually. A safety feature incorporated in the design of the
trigger mechanism prevented 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
![P-39Q Airacobra weapons bay](https://upload.wikimedia.org/wikipedia/commons/6/68/P-39Q_Airacobra_weapons_bay.jpg)
The 37 mm cannon was disliked by pilots for its low muzzle velocity, resulting in more pronounced drop than other contemporary weapons.
The only standard aircraft armed with the M4 to see service were the
Bell P-39 Airacobra
The Bell P-39 Airacobra is a fighter produced by Bell Aircraft for the United States Army Air Forces during World War II. It was one of the principal American fighters in service when the United States entered combat. The P-39 was used by the ...
and the derivative
P-63 Kingcobra
The Bell P-63 Kingcobra is an American fighter aircraft that was developed by Bell Aircraft during World War II. Based on the preceding Bell P-39 Airacobra, the P-63's design incorporated suggestions from P-39 pilots and was superior to its pr ...
. It was used as a limited standard aircraft in North Africa and the Pacific theater by the USAAF and Allied air forces.
Some YP-38s, the prototype model of the
P-38 Lightning
The Lockheed P-38 Lightning is an American single-seat, twin piston-engined fighter aircraft that was used during World War II. Developed for the United States Army Air Corps by the Lockheed Corporation, the P-38 incorporated a distinctive tw ...
, mounted a single M4 before the armament scheme was finalized.
Production Lightning models would replace the M4 with the
AN/M2 20 mm cannon.
The experimental
XP-58 "Chain Lightning" was a larger, more heavily armed version of the P-38 Lightning equipped with quadruple M4 cannons instead of M2 heavy machine guns in its nose. Its original purpose (like the German
Bf 110
The Messerschmitt Bf 110, often known unofficially as the Me 110,Because it was built before ''Bayerische Flugzeugwerke'' became Messerschmitt AG in July 1938, the Bf 110 was never officially given the designation Me 110. is a twin-engine (Des ...
) 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 single
75mm M5 cannon and a pair of .50 caliber heavy machine guns.
The first US jet, the
P-59 Airacomet
The Bell P-59 Airacomet was a single-seat, twin jet-engine fighter aircraft that was designed and built by Bell Aircraft during World War II, the first produced in the United States. As the British were further along in jet engine developme ...
, mounted a single M4 cannon in the nose, along with three .50 caliber machine guns.
US Navy
![37mm T9 cannon](https://upload.wikimedia.org/wikipedia/commons/f/f6/37mm_T9_cannon.jpg)
The M4 37 mm (1.46 in) automatic cannon was mounted on numerous
U.S. Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage of ...
PT boat
A PT boat (short for patrol torpedo boat) was a motor torpedo boat used by the United States Navy in World War II. It was small, fast, and inexpensive to build, valued for its maneuverability and speed but hampered at the beginning of the wa ...
s as deck guns, beginning with the
Solomon Islands campaign
The Solomon Islands campaign was a major campaign of the Pacific War of World War II. The campaign began with Japanese landings and occupation of several areas in the British Solomon Islands and Bougainville, in the Territory of New Guinea, du ...
. 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 the
Soviet Air Forces
The Soviet Air Forces ( rus, Военно-воздушные силы, r=Voyenno-vozdushnyye sily, VVS; literally "Military Air Forces") were one of the air forces of the Soviet Union. The other was the Soviet Air Defence Forces. The Air Forces ...
with the M4-equipped P-39 ''Airacobra'' and P-63 ''King Cobra''. The U.S did not supply M80 armor-piercing rounds for these
Lend-Lease
Lend-Lease, formally the Lend-Lease Act and introduced as An Act to Promote the Defense of the United States (), was a policy under which the United States supplied the United Kingdom, the Soviet Union and other Allied nations with food, oil, ...
aircraft—instead, the Soviets received 1,232,991 M54 high-explosive rounds. The M4 was sometimes employed against soft ground targets on the
Eastern Front but 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. 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).
[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. .]
US-built contemporaries and successors
* The 37 mm M9 autocannon was a derivative of the
37 mm M1A2 flak 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.
George Chinn
George Morgan Chinn (January 15, 1902September 4, 1987) was an American weapons expert and soldier. He attended Centre College, and played on the 1921 Centre Praying Colonels football team, which won the national championship. Chinn then opened a ...
1951, 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 Little is known about this gun's deployment; the only confirmed use is in the US Navy PT boats mentioned above.
* The 37 mm M10 autocannon was 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.
The M10 replaced the M4 in aircraft starting with the A-9 model of the
Bell P-63 Kingcobra
The Bell P-63 Kingcobra is an American fighter aircraft that was developed by Bell Aircraft during World War II. Based on the preceding Bell P-39 Airacobra, the P-63's design incorporated suggestions from P-39 pilots and was superior to its pr ...
.
The disintegrating link belt made it possible to increase ammunition storage in the
Bell P-63 Kingcobra
The Bell P-63 Kingcobra is an American fighter aircraft that was developed by Bell Aircraft during World War II. Based on the preceding Bell P-39 Airacobra, the P-63's design incorporated suggestions from P-39 pilots and was superior to its pr ...
from 30 rounds to 58 rounds.
See also
*
List of U.S. Army weapons by supply catalog designation
This is a historic (index) list of United States Army weapons and materiel, by their Standard Nomenclature List (SNL) group and individual designations — an alpha-numeric nomenclature system used in the United States Army Ordnance Corps Supply ...
*
COW 37 mm gun
The COW 37 mm gun was a British automatic cannon that was developed during First World War as a large-calibre aircraft weapon. It was tested in several installations and specified for the Westland C.O.W. Gun Fighter for attacking bombers. Th ...
: earlier British equivalent
*
M4 carbine
The M4 carbine (officially Carbine, Caliber 5.56 mm, M4) is a 5.56×45mm NATO, gas-operated, magazine-fed carbine developed in the United States during the 1980s. It is a shortened version of the M16A2 assault rifle.
The M4 is extensively ...
Weapons of comparable role, performance and era
*
Nudelman-Suranov NS-37
The Nudelman-Suranov NS-37 (russian: Нудельман - Суранов НС-37) was a aircraft cannon, which replaced the unreliable Shpitalny Sh-37 gun. Large caliber was planned to allow destruction of both ground targets (including armoured ...
(
Nudelman N-37
The Nudelman N-37 was a 37 mm (1.46 in) aircraft autocannon used by the Soviet Union. It was designed during World War II by V. Ya. Nemenov of A.E. Nudelman's OKB-16 to replace the earlier Nudelman-Suranov NS-37 and entered service in 1 ...
): Soviet equivalents
*
Vickers S gun
The Vickers 40 mm Class S gun, also known simply as the "S gun", was a 40 mm (1.57 in) airborne autocannon designed by Vickers-Armstrongs for use as aircraft armament.
It was primarily used during World War II by British aircr ...
: 40mm British equivalent
*
''Bordkanone'' BK 3,7: German equivalent
*
Ho-203 cannon
Ho-203 was a Japanese autocannon that saw considerable use during World War II. It was a long-recoil automation of the Year 11 Type direct-fire infantry gun. It was fed by a 15-round closed-loop ammunition belt. It was operationally used only as ...
: Japanese equivalent
Notes
References
* War Department,
U.S. Army
The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cl ...
Coast Artillery Corps
The U.S. Army Coast Artillery Corps (CAC) was an Corps#Administrative corps, administrative corps responsible for coastal defence and fortification, coastal, harbor, and anti-aircraft Seacoast defense in the United States, defense of the United S ...
, Training Manual TM-9-2300 ''Standard Artillery and Fire Control Materiel'' (7 February 1944)
* War Department, Training Manual TM 9-240 ''37-mm Aircraft Gun Materiel M4'' (30 March 1942)
* War Department, Training Manual TM 9-1240 ''37-mm Automatic Gun M4 (Anti-aircraft)'' (3 January 1942)
* War Department,
US Army Ordnance Corps,
Standard Nomenclature List Catalog, Group A, Subgroup A46 ''ORD SNL A-46 (37mm Gun, Automatic, models M4 & M10)''
P-63 KingCobra - Browning M4 37mm Auto Cannon Gun
External links
* {{Commons category-inline, M4 cannon
37 mm artillery
Aircraft guns
Autocannon