Author: Joshua Allen

105 mm Howitzer Motor Carriage M37

Post author By Joshua Allen
Post date July 27, 2024
4 Comments on 105 mm Howitzer Motor Carriage M37

M37 105mm Howitzer Motor Carriage. Illustration made by by Ardhya ‘Vesp’ Anargha.

United States of America (1945-Late 1950s)
Howitzer Motor Carriage – 316 Built

The 105 mm Howitzer Motor Carriage M37 (HMC) represented a step forward in artillery technology, envisioned as the successor to the widely utilized M7 Priest sporting a similar 105 mm howitzer gun, but on the more modern M24 Chaffee chassis. Despite being adopted, the end of the Second World War curtailed the M37’s widespread utilization. While initially slated to replace its predecessors, boasting mobility and modernized features, the M37’s deployment remained limited, never fully replacing the previous self-propelled guns and getting quickly taken out of service itself due to a change in doctrine due to the need to seal vehicles for nuclear war.

A three-quarter view of an M37 at Aberdeen Proving Ground on 29 July 1945. Image source: Development History of 105mm Gun & Howitzer Motor Carriages and 25-pdr Gun Motor Carriage

The Beginning

The M37 HMC was designed to fill the need for a lightweight and high-speed mobile artillery platform to replace the M7 HMC. The M7 HMC Priest, which started production in April 1942, was vulnerable when used in close support because it had no direct fire sight, inadequate ammunition protection, and thin frontal armor. However, despite this, it continued to serve into the Korean War. This led to the development of other howitzer-armed vehicles, including the M4 105 mm, M4A3 105 mm, M8 Scott, and M37 HMCs.

An M7 Priest preserved on the entrance road inside Aberdeen Proving Ground (Maryland). Image source: https://commons.wikimedia.org/wiki/File:M7_Priest_at_APG.jpg

Between January and February 1943, various studies were performed on the T16 4.5 inch (11.4 cm) GMC (Gun Motor Carriage), based on a lengthened M5 light tank chassis, by the Field Artillery Board and Aberdeen Proving Ground. It was found that it was less expensive, weighed less, and was more mobile than the M7 HMC. However, the howitzer mounted on the rear of the vehicle caused the gun to need to be “excessively high” to allow for the desired 10° of depression and would cause the T16 to be back heavy. This meant that it would not be adopted. Additional studies showed that exchanging the gun for a 105 mm howitzer mounted in the rear would, while maintaining “good all round armor”, give the desired traverse range while allowing it to be used in direct and indirect fire roles.

The T16 4.5 inch GMC (Gun Motor Carriage). Image source: Stuart – A history of the American light tank

Work Starts

During July 1943, work on the procurement of a pilot vehicle for a 105 mm Howitzer Motor Carriage based on the T24 light tank, the pilot vehicle for the M24, started, designated T76 105mm Howitzer Motor Carriage (T76 105 mm HMC). The T24 was likely chosen as it was bigger than the earlier M3 and M5 Stuart light tanks.

The M24 Chaffee (designated Light Tank, M24) was initially designed in 1943, with the pilot being delivered on 15 October 1943, and entered service in 1944. The M24 was created to replace the earlier obsolete M3 and M5 Stuart light tanks. These did not have sufficient armament to effectively combat most tanks, and, as such, the M24 was armed with a 75 mm M6 gun and an M2HB 12.7 mm (0.5 in) machine gun which was a vast improvement over the M3 and M5’s 37 mm gun.

The T24 pilot model in 1943. Image source: http://www.m24chaffee.com/prototype—t24.html

On 10 June 1943, the Ordnance Council, in OCM 20679, recommended a pilot vehicle, designated 105 mm howitzer motor carriage T76, be developed and procured. A wooden mock-up of the T76 was created and subsequently reviewed by the Artillery Officers from the Ordnance Board. They advised that the vehicle was to be used as mobile artillery to support the proposed light tank units and subsequently needed a high rate of fire.

To allow for the desired rate of fire, the crew was increased from six to seven, and the size of the fighting compartment was increased. This allowed the crew to work efficiently without unnecessary interference while staying within the armor. The size of the fighting compartment was increased by relocating the engine to the rear instead of the middle. This added 30.5 cm (12 in) to the fighting compartment. A total of 12.7 mm (0.5 in) of armor was used throughout the design. The assistant driver was removed, likely so that the gun mount could be moved to be centrally located and moved forward, lengthening and increasing the fighting compartment by 15.3 cm (6 in). This also allowed the anti-aircraft ring mount to be placed to the driver’s right, where the co-driver’s hatch was previously located.

A top down view of the T76. Image source: Catalog of Standard Ordnance Items, second edition 1944, volume I: Tank and Automotive

Due to an inspection by the Ordnance Board, a new mock-up was created in September 1943, and a gun crew from the Armored Command assessed various stowage arrangements using different heights and amounts of equipment. After the best arrangement had been found, later in September, the updated mock-up was reviewed by representatives from the Army Ground Forces, the Armored Board, and the Tank-Automotive Center. The representatives approved of the mock-up’s arrangement and requested at least two pilot models with the same characteristics so that they could be tested. During December 1943, the Army Services Force decided to approve the characteristics to be implemented on the T76 105 mm HMC.

A top-down view of a T76. The ammunition is stored vertically. Image source: https://en.topwar.ru/88311-samohodnaya-artilleriyskaya-ustanovka-m37-howitzer-motor-carriage-ssha.html

To speed up the delivery of the pilot vehicles, the Tank-Automotive Center designed and procured the gun mount. This work was finished, and the Gun Mount T14 was proof fired on 17 March 1944, at which point malfunctions were recorded, modifications subsequently applied, and the design of the necessary additional or replacement parts was started. The resultant changes were implemented, and the new mount had reinforcements welded on to attach the mount to the vehicle. This caused the maximum elevation to decrease from 45° to 42°. The Armored Board approved this and was still present in production vehicles. The elevating mechanism was redesigned to allow for an improved support pad and increased elevation radius. In addition, modified sleeves or throttling groves were created and placed into the recoil cylinders.

The T76 105 mm HMC pilot No 1 on 15 July 1944. The canvas cover and other weatherproofing has been fitted. Image source: Development History of 105mm Gun & Howitzer Motor Carriages and 25-pdr Gun Motor Carriage

This new mount was tested at the Rock Island Ordnance Center (Illinois) sometime between 4 and 11 June 1944 and was found to be very satisfactory. After this, the vehicle was sent to Aberdeen Proving Ground (Maryland) to perform extended firing tests, which also checked the fire control equipment. These tests found the design to be satisfactory, provided the following issues were rectified:

When operating with all hatches closed and canvas cover in place, the temperature was too high for the crew to operate.
The gun’s recoil guard was too short, endangering the crew.
The breech block opened due to the operating handle unlatching, which made it hard for the loader to remove the shell casing.
When traversing right, the interphone communication control box would block the traverse wheel, limiting the traverse.
The inner gun shield would bend, which rubbed against the opening, preventing the gun from easily elevating and depressing.
The Panoramic Sight Mount T96 loosened and had excess dispersion when firing.
The travel lock was unsatisfactory.

After the tests at Aberdeen Proving Ground, Pilot No1 was sent to Armored Command at Fort Knox (Kentucky) for automotive tests, including stowage requirements. The design was well-liked and was found to be superior to the M7 HMC. Some of the superior factors included fuel economy, climbing slopes, and armor protection. After these tests, Pilot No1 was returned to Rock Island Ordnance Center to fit a modified gun mount, fire control, gun travel lock, and other minor modifications.

The front of the T76, the T14 gun mount and the initial M2HB Anti-Aircraft mount are visible. Image source: https://en.topwar.ru/88311-samohodnaya-artilleriyskaya-ustanovka-m37-howitzer-motor-carriage-ssha.htm

After Pilot No1 was returned to Rock Island Ordnance Center, Pilot No2 was sent as well to receive the same modifications. After this, it underwent firing tests at Aberdeen Proving Ground. It was then sent to the American Car and Foundry Company to be reworked, including replacing the M49C machine gun ring mount for the T107 anti-aircraft ring mount, the elimination of the SCR 510 (to provide space for more 105 mm ammunition), redesigning the rear hull door to act as a loading ramp, and the ammunition stowage being changed by stowing the rounds horizontally increasing from 68 to 128 rounds. After this, it served as a model for production drawings. After these changes, the T76 was standardized as the 105 mm Howitzer Motor Carriage M37.

The second T76 pilot, at Aberdeen Proving Grounds during summer 1945, which was later standardized as the M37. Image source: https://en.topwar.ru/88311-samohodnaya-artilleriyskaya-ustanovka-m37-howitzer-motor-carriage-ssha.html

The rear of T76 Pilot No1 on 15 July 1944, showing how the canvas cover was attached. Image source: https://en.topwar.ru/88311-samohodnaya-artilleriyskaya-ustanovka-m37-howitzer-motor-carriage-ssha.html

The rear of an M37 in use at Aberdeen Proving Ground on 29 July 1945. Image source: Development History of 105mm Gun & Howitzer Motor Carriages and 25-pdr Gun Motor Carriage

Production

An M37 being trialed in 1945 in the Mojave Desert (California). With so much sand stuck to the vehicle, it appears almost white. Image Source: https://www.m24chaffee.com/m37-original-period-photos-us-military.html

A production order for 750 vehicles was issued on 12 December 1944, to be completed before 31 December 1945. This was later reduced to only 448, likely due to the end of the war. With the sighting and fire control equipment standardized during July 1944, production started in January 1945 and lasted until 1953. Around 316 M37s were actually produced out of the 448 ordered, with around 150 produced post-war by American Car & Foundry and the remainder produced by Cadillac and Massey-Harris, likely starting during World War 2. However, some sources, in particular R. P. Hunnicutt, state that only 150 were built, but this could be a confusion with which manufacturers created the vehicles. However, no serial numbers above 150 could be found during research.

Design

Various drawings from technical manuals showing the component parts.
Image Source: http://www.m24chaffee.com/m37-105mm-hmc–information.html

Dimensions

The M37 was 5.49 m (6 yd) long, 3 m (3.28 yd) wide, and 2.84 m (3.11 yd) tall.

The M37 HMC’s dimensions. Image Source: FM 6-76

Armor

The armor was made of 9.53 mm to 12.7 mm of rolled homogeneous steel, which was welded together.

Plate	Thickness		Angle
	(mm)	(inches)	(all angles are from the vertical)
front top	12.7 mm	0.5 in	90°
front floor	12.7 mm	0.5 in	90°
upper front	12.7 mm	0.5 in	60°
lower front	12.7 mm	0.5 in	45°
lower rear	12.7 mm	0.5 in	45°
front sides	12.7 mm	0.5 in	12°
fighting compartment	12.7 mm	0.5 in	0°
upper rear	12.7 mm	0.5 in	0°
howitzer shield	12.7 mm	0.5 in	0° to 38°
rear floor	9.53 mm	0.375 in	90°

Armament

The M37 was armed with an M4 105 mm Howitzer, descended from the towed M2A1 Howitzer. The M4 Howitzer was initially designed to fit in the M4 Sherman’s turret in an M5 mount in the front of the hull. Compared to the M2A1, the M4 has a modified breech and a cylindrical recoil surface.

The M2A1 Howitzer. Image Source: https://www.baiv.nl/1942-m2a1-105-mm-howitzer-the-workhorse-of-the-field-artillery-for-the-u-s-army-in-wwii/

The M4 Howitzer had a fire rate of eight rounds per minute. In the M37 HMC, the M4 Howitzer could manually traverse 51.7°, 25.4° to the left and 26.3° to the right. Elevation was from -10.5° to +42.8°. The howitzer had very little overhang forward and a fire height of 1.7 m (1.83 yd).

The main gun used one of each of the following:

T92 Periscopic Sight, which made direct fire easier
M12A2 Panoramic telescope (with an M19 light instrument), normally used to lay the weapon on the azimuth for indirect fire
M76G Telescope (on T96 Telecop mount, with an M33 light instrument)
M1 Gunner Quadrant, used to lay elevation and measuring angles of elevation
T14 Range Quadrant (with an M18 light instrument)
M1 Aiming Post
M14 Light Aiming Post
M22 Fuse Setter

The gun could fire a variety of shells, including: the M1 HE (High-Explosive), M67 HEAT (High-Explosive Anti-Tank), M84 smoke (white or colored), M60 white phosphorus or mustard gas, M1 empty shell, and the M14 Drill cartridge. On board, there were 126 rounds, of which 6 were ready to fire.

M4 Howitzer Rounds fired from the M37 HMC
Type	Model	Weight of the round	Length of the round	Warhead Contents	Muzzle velocity	Range (at 44º)
HE	M1 HE Shell	19.08 kg (42.07 lb)	78.87 cm (31.05 in)	TNT or an equal mix of TNT and amatol	472 m/s (1,550 ft/s)	11,160 m (12,205 yd)
HEAT	M67 HEAT
Smoke, white	M84 HC BE Shell	19.02 kg (41.94 lb)	80 cm (30.49 in)	HC (Zinc chloride) smoke mixture	472 m/s (1,550 ft/s)	11,160 m 12,205 yd
Smoke, colored	M84 BE Shell	Green, Violet: 17.95 kg 39.57 lb Red 18.04 kg 39.77 lb Yellow 17.86 kg 39.37 lb		Various Smoke mixtures 44.38 lb	Likely greater than 472 m/s (1,550 ft/s)	Likely greater than 11,160 m (12,205 yd)
Smoke	M60 WP Shell	19.83 kg (43.71 lb)	78.94 cm (31.08 in)	White phosphorus	472 m/s (1,550 ft/s)	11,160 m (12,150 yd)
Smoke	M60 FS Shell	19.2 kg (42.32 lb)	Likely around 78.94 cm (31.08 in)	White phosphorus	Likely around 472 m/s (1,550 ft/s)	11,160 m (12,150 yd)
Chemical	M60 H Shell	Likely around 19.2 kg (42.32 lb)	Likely around 78.94 cm (31.08 in)	Mustard gas	Likely around 472 m/s (1,550 ft/s)	11,160 m (12,150 yd)
Practice	M1 Empty Shell	2.83 kg (6.23 lb)	15.24 cm (6 in)	No warhead it had a 0.68 kg (1.5 lb) or 2 lb (0.91 kg) charge the rest was filled with sand	N/A	N/A
Drill	M14 Drill Cartridge	18.76 kg (41.35 lbs)	78.92 (31.07 in)		N/A	N/A
Blank		2.83 kg (6.23 lbs)		M15 Cartridge Case wth No warhead it had a 2 lb (0.91 kg) charge	N/A	N/A

Top-down views of the M37 without ammunition. Image source: ORD 9 SNL G-236 via https://afvdatabase.com/usa/105mmhmcm37.html

The front right of the M37’s fighting compartment, with a view of the gun and driver’s compartment. Image source: https://imgur.com/a/DJMk2

The M37’s fighting compartment, with the breechblock on the left and radiator air inlet grilles on the right visible. One of the torsion bars is visible due to the floor of the fighting compartment being absent. Image source: http://afvdb.50megs.com/usa/pics/105mmhmcm37/105mmhmcm37.html

The vehicle had a 12.7 mm (0.50 in) Browning M2HB machine gun, which was primarily for anti-aircraft use. This was mounted on the front left of an M68 Concentric Ring Mount, which allowed the gun to manually traverse 360°. There were 990 stowed rounds, likely stowed in the sponsons.

The vehicle initially carried one 0.45 caliber submachine gun, likely an M3 or M3A1 “Grease Gun”, with 750 rounds and four 0.30 caliber carbines, likely the M1 model. However, this was likely changed to either all M3 submachine guns or four M3 submachine guns and one M1 0.30 carbine later in the vehicle’s life.

A view of the front of an M37 at Aberdeen Proving Ground on 29 July 1945. Image source: Development History of 105mm Gun & Howitzer Motor Carriages and 25-pdr Gun Motor Carriage

The howitzer’s travel lock and its component parts (left). The M68 91 cm (36 in) diameter concentric ring mount, with the barrel being stored in the barrel clip (right). Image Source: ORD 9 SNL G-236 via https://afvdatabase.com/usa/105mmhmcm37.html

Automotive and Performance

The M37’s performance capabilities. Image Source: FM 6-76

The vehicle used a liquid-cooled two 8-cylinder Cadillac Series 44T24 engines, with a net horsepower of 220 hp@3,400rpm and a gross horsepower of 296 hp@3,200rpm. The engine developed a net torque of 480 ft-lb@1,200rpm and a gross torque of 560 ft-lb@1,200rpm. The electrical system ran at 24 volts at 3,000 watts with a 50 amp panel set. The vehicle had an unloaded weight of 17.2 tonnes (19 tons) and a combat weight of 25 tonnes (23.1 tons). The engine held 9.09 liters (8 quarts) of engine oil and 45.5 liters (40 quarts) of coolant for the entire system.

The M37 had a fuel capacity of 416.4 liters (110 gallons) of 80-octane gasoline in two tanks, each holding half the fuel. These were located on either side of the engine compartment.
Steering was through a controlled differential with steering levers, the brakes were mechanical external contracting, and the transmission was a herringbone gear, twin hydramatic, with 8 speeds forward and 4 in reverse. Each engine and transmission assembly weighed 529 kg (1,166 lbs).

The M37’s engine deck and its components. Image source: ORD 9 SNL G-236 via https://afvdatabase.com/usa/105mmhmcm37.html

The top speed on road was 56 km/h (35 mph), with a cruising range of around 161 km (100 mi) on road and a turning circle of 12.2 m (40 ft). The maximum length of trench it could cross was 2.44 m (8 ft). It had a climbing grade ascending ability of 60° and could cross a step of 1 m (3.3 ft). It had a bridging weight of 17.7 tonnes (19.5 tons), and a fording depth of 2.13 m (7 ft) when waterproofed. The fire protection system consisted of a 4.54 kg (10 lb) C02 fixed fire extinguisher and a 1.81 kg (4 lb) one.

The M37’s engine and its components parts. The text is adapted from ORD 9 SNL G-236.
A. left elbow; B. tank, assembly (complete); C. conduit and cable, assembly; D. pump, assembly (complete); E. bushing; F. nipple; G. plug; H. neck; J. cap, assembly; K. valve; L. hose: M. tee: N. elbow; P. elbow; Q. nipple; R. valve; S. screw/washer; T. conduit; U. absorber; V. boot; W. conduit; X. grommet; Y. Hose; Z. tube; AA. conduit; BB. clip; CC. clamp; DD. tee; EE. hose; FF. hose: GG. inlet; HH. radiator; JJ. tube; KK. hose; LL. conduit and cable, assembly; MM. tank, assembly (complete); NN. right elbow; PP. right elbow; QQ. carburettor; RR. cleaner; SS. shaft; TT. filter, assembly; UU. left elbow. Image Source: ORD 9 SNL G-236 via https://afvdatabase.com/usa/105mmhmcm37.html

The front of the radiator air inlets on an M37. Image Source: ORD 9 SNL G-236 via https://afvdatabase.com/usa/105mmhmcm37.html

Suspension

The suspension consisted of torsion bars with five individually sprung dual road wheels, with the first two and last two road wheels with shock absorbers. The tyre size on the road wheels was 57.2 cm (22.5 in) by 11.4 cm (4.5 in). The drive sprockets had 13 teeth, the idlers were at the rear, and four return rollers held the upper part of the track. The size of the idler was 57.2 cm (22.5 in) by 12.7 cm (5 in). The tread was 2.4 m (2.67 yd), and the ground clearance was 46 cm (0.5 yd). The ground pressure with the T72 tracks was 0.814 kg/cm² (11.6psi). The track used 80 track links with a ground contact length of 3.15 m (124 in), with a pitch of 78.7 mm (5.5 in).

There were two main types of tracks, T72 and T85E1. The T72 were steel and rubber bushed with a single pin that used parallel grousers. The T85E1 used a rubber chevron contact pad, the rest being steel, with a double pin with a center guide. When using the T72 track, the track width was 40.6 cm (16 in). When using the T85E1 track, the track width was 35.6 cm (14 in) without extended-end connectors and 41.9 cm (16.5 in) with extended-end connectors.

Crew

In April 1945, the M37 HMC had a crew of 7: a chief of section in the left of the hull, a gunner in the left rear of the hull, four cannoneers (the artillery term for loader), and a driver in the front left of the hull beside the gun.

The crew’s positions when not in combat (left) and the crew’s positions when in action (right). CS = chief of section, G = gunner, D = driver, and 1-4 = cannoneers. Image Source: FM 6-76, the author has retouched the images.

After October 1952, the crew was increased to 8 with an additional cannoneer, likely to increase the fire rate.

The crew communicated using an M238 flag set and, after October 1947, using 3 RC99 radios. There was an option to install a British No. 19 wireless set if 24 rounds of ammunition were removed.

The M37 driver’s compartment. Image Source: https://imgur.com/a/DJMk2

Experiments

M37 with a Recoilless Rifle

Throughout 1945, the US launched a series of projects to develop vehicles that wielded a recoilless weapon. The first experiments on the M37 HMC chassis began in spring 1945, with the first project replacing the M2HB with a T21 75 mm recoilless rifle. The main disadvantage of this arrangement lay in the fact that the recoilless rifles had excessive backblast, which could injure the crew. This meant that the recoilless rifle could only be fired in certain directions to prevent the powerful exhaust blast from going into the vehicle due to the open top. In addition to this, these possible fire directions were not the most effective. The vehicle was canceled on 2 October 1947, being replaced by an M19 with four recoilless rifles instead of the anti-aircraft mount.

The M37 showing the 75 mm recoilless rifle. Image source: https://en.topwar.ru/88520-rannie-amerikanskie-proekty-sau-s-bezotkatnymi-orudiyami.html

T38 Mortar Motor Carriage

The T38 was designed by the York Safe and Lock Company of York, Pennsylvania to provide a kit to convert the M37 to a mortar carrier, possibly to extend the life of the M37. The plans were then transferred to Detroit Arsenal, where one was converted and taken to Aberdeen Proving Ground in December 1945. The trials lasted until 1949, but the vehicle was not accepted into production, as self-propelled mortars had fallen out of favor.

The T38, an M37 with an M4 mortar. Notice the baseplate mounted where the gun previously was. Image source: https://www.tankarchives.ca/2019/09/a-fast-howitzer-on-light-chassis.html

The T38 MMC had an M4 10.7 cm (4.2 in) mortar mounted instead of the howitzer. The howitzer opening was closed off, as the mortar fired through the open roof. The T38 was similar to the M21 Mortar Motor Carriage, as the mortar was installed in the fighting compartment and could be fired from within the vehicle or outside the vehicle using a baseplate. A beam was placed along the bottom of the hull at the rear to support the mortar. The weight was decreased to 17.5 tonnes (17.2 tons), and it carried 140 mortar rounds. The vehicle’s crew was reduced to six. These would have included an assistant mechanic to man the mortar with the other crew members. The ammunition was stored in the fighting compartment. The mortar used a screw rotation mechanism which gave 90º of traverse to either side. The elevation of the mortar had a range from 45º to 60º.

The interior of the T38 with a top-down view (left) and a view of the mortar (right). Image Source: Stuart – A history of the American light tank

Service

The M37 entered service in 1945 likely around April or within the first six months, however, it was too late to be deployed in the Second World War.

An M37 nicknamed “Hell Fire” being used by the 58th Field Artillery Battalion, 3rd Infantry Division attacking a Chinese position next to the Imjin River, Korea on 12 April 1951. Image source: https://warspot.net/430-hmc-m37-a-fast-howitzer-on-a-light-chassis

An M37 beside other self-propelled guns of the period, the M41, M40, M12, and T92. Notice the increasing number of crew and larger guns. Image Source: http://www.m24chaffee.com/m37-original-period-photos-us-military.html

The only limited US combat deployment of the M37 happened during the Korean War, which lasted from 1950 to 1953. There, they were used to support the infantry as mobile artillery and to attack enemy positions. The M37 served in the 58th Armored Field Artillery Battalion (a primarily black segregated unit until 16 October 1951 when it was integrated), which was attached to the 65th Infantry Regimental combat team; however, it was converted to use towed howitzers and redesignated the 58th Field Artillery Battalion on 10 November 1951. This meant that the M37 served in Korea for around a year; some areas the M37 fought were near the Imjin River and Han River.

An M37 belonging to the 501st Field Artillery, B Company, 8th Vehicle. This appears to be an all-black segregated unit, possibly in the Korean War. The two men in the foreground signed the image. Image Source: https://www.flickr.com/photos/rich701/21280764956/in/photostream/

A pair of M37s firing on Chinese soldiers located north of the Han River. Image Source: Armor In Korea A Pictorial History by Jim Mesko

The M37 also served with the US forces in West Germany, likely being there until around 1957, including with the 30th Field Artillery Group and the 3rd, 14th, 70th, 74th, 78th and 517th Armored Field Artillery Battalions.

An M37 belonging to the 3rd Armored Field Artillery Battalion rumbles through a German village during the early 1950s. Image Source: https://www.usarmygermany.com/Units/2nd%20Armd%20Div/3rd%20AFA%20Bn%20105mm%20SP%20howitzers%20roll%20through%20a%20small%20German%20town%20duringa%20fiel%20exercise%20600.jpg

An M37 during action or an exercise in the early 1950s in Germany. Image Source: https://www.m24chaffee.com/m37-original-period-photos-us-military.html

The M37 likely started to exit service in the late 1950s, after the M52 entered service. It remained active with the National Guard and Reserve units until the early 1960s. The M37 was superseded by the M52, a turreted self-propelled gun based on the M41 light tank which offered better protection for the crew, particularly as it could be sealed if fighting in a dangerous environment, such as the one created by the envisioned use of nuclear or chemical weapons.

An M52, the vehicle that succeeded the M37 in service. Image Source: https://www.armedconflicts.com/M52A1-105-mm-samohybna-houfnice-t226802

Other Users – Spain

Spain likely received 28 M37 HMCs (although some English-language sources, such as M24 Chaffee Light Tank 1943-85 state 36). The first three vehicles arrived on 7 January 1957 in the port of Cartagena. These went to the Regimiento de Artillería a Caballo nº19 (Horse Artillery Regiment No 19) of the División de Caballería ‘Jarama’ (Jarama Cavalry Division). An additional vehicle arrived in June, and the remaining 28 in 1958. Twelve of these were used to complement the existing ones at the Regimiento de Artillería a Caballo nº19 with four M37s per battery. Another twelve were given to the Regimiento de Artillería de Campaña nº13 (Field Artillery Regiment No 13). The Artillery Academy received the remaining 4 M37 for training.

After the Regimiento de Artillería a Caballo nº19 was dissolved, its M37s were transferred to the Grupo de Artillería de Campaña Autopropulsada XI (Self-Propelled Field Artillery Group XI). Similarly, the twelve M37s of the Regimiento de Artillería de Campaña nº13 were transferred to the Grupo de Artillería de Campaña Autopropulsada XII (Self-Propelled Field Artillery Group XII). Both the XI and XII belong to the Brigada Acorazada ‘Brunete’ (Brunete Armored Brigade). Around six survive in museums.

A Spanish M37 during a military exhibition with a three-tone camouflage pattern. Image Source: Marín Gutiérrez & Mata Duaso (2005), p. 107

Surviving M37

Many M37 HMCs have managed to survive to this day.

US

The US has eighteen surviving M37, mostly in good condition, in the following locations:

Georgetown, Massachusetts
Vestal, New York (nicknamed “CarolAnn”)
Fort Lee U.S. Army Ordnance Museum, Virginia (serial number 75)
American Armored Foundation, Tank Museum, Danville, Virginia
Liberty, North Carolina
National Armor and Cavalry Museum, Fort Benning, Georgia (serial number 37)
3rd Infantry Division Museum, Fort Stewart, Georgia
Georgia Army National Guard Armory, Savannah, Georgia
Gainesville, Florida
Institute of Military Technology, Titusville, Florida (previously exhibited in the World War II Vehicle Museum and Learning Center in Hubbard, Ohio)
Carleton, Michigan
Russell Military Museum, Russell, Illinois
US Army Artillery Museum, Fort Sill, Oklahoma (came from Fort Drum and arrived in 1966)
Russell Military Museum, Russell, Illinois
American Society of Military History “Tankland”, South El Monte, California (incomplete)

Serial number 115 survives and was once at the John W. Rich Auto Museum, Reading, Pennsylvania, but was likely sold to an unknown buyer in 2014.

Two of the surviving M37 in the US, one was once in the John W. Rich Auto Museum (Top), and the other in MERDC (Mobility Equipment Research and Design Command) camoflash scheme in the Georgia Army National Guard Armory, Savannah (Georga) (Bottom). Image Source: https://www.m24chaffee.com/m37-survivors—restored—unrestored.html, http://the.shadock.free.fr/Surviving_M37_HMC.pdf

Spain

Five M37s survive in Spain: one in El Goloso Museum (Madrid) and four at various locations in Zaragoza.

Two of the surviving M37 in Spain, in El Goloso (Top) and Zaragoza (Bottom). Image Source: https://www.m24chaffee.com/m37-survivors—restored—unrestored.html, http://the.shadock.free.fr/Surviving_M37_HMC.pdf

Conclusion

The M37 emerged as an improved artillery platform, born out of the necessity for a lightweight, high-speed mobile solution to replace its predecessor, the M7 Priest. Through meticulous development and rigorous testing, the M37 evolved into a useful tool which was too late to serve in World War 2, but served in the Korean War, boasting a blend of firepower, mobility, and crew protection. Over time, the M37’s role continued beyond wartime theaters, serving in West Germany and continuing its duty with National Guard and Reserve units well into the early 1960s. Internationally, the M37 found a new home in Spain, where it contributed to their artillery regiments.

M37 105mm Howitzer Motor Carriage. Illustration made by by Ardhya ‘Vesp’ Anargha.

M37 in MERDC (Mobility Equipment Research and Design Command) camouflage scheme. Illustration made by by Ardhya ‘Vesp’ Anargha.

A Spanish M37 with a three-tone camouflage pattern. Illustration made by by Ardhya ‘Vesp’ Anargha.

M37 Specifications
Dimensions (LxWxH)	Length: 5.49 m (6 yd) Width: 3 m (3.28 yd) Height: 2.84 m (3.11 yd)
Track width	T72: 40.6 cm (16 in) T85E1: 35.6 cm (14 in)
Total Combat Weight	25 tonnes (23.1 tons)
Crew	Originally 7 Later 8
Engine	two 16-cylinder Twin Cadillac Series 44T24 220 hp
Maximum speed	56 km/h (35 mph)
Suspension	Torsion bar
Range	161 km (100 mi)
Armament	105 mm M4 howitzer .50 caliber M2HB machine gun
Armor	9.53 mm (0.375) to 12.7 mm (0.5 in)

Sources

E J Zawadzki (compiled by), Development History of 105mm Gun Howitzer Motor Carriages and 25-pdr Gun Motor Carriage, Office of the Chief of Ordnance, 9 March 1945
FM 6-76: Service Of The Piece 105mm Howitzer Motor Carriage, M37, War Department, 15 April 1945
TM 9-1901 ARTILLERY AMMUNITION, WAR DEPARTMENT, 29 June 1944

RP Hunnicutt, Stuart – A history of the American light tank, Presidio Press, Novato, 1992
Steven J. Zaloga, 077 – M24 Chaffee Light Tank 1943-85, Osprey Publishing, New York, 2003
Jim Mesko, M24 Chaffee in action: armor no 25, Squadren /Signal Publications inc, Carellton, 1988
Jim Mesko, Armor in Korea A Pictorial History, Squadren /Signal Publications inc, Carellton, 1984
Francisco Marín Gutiérrez & José Mª Mata Duaso, Carros de Combate y Vehículos de Cadenas del Ejército Español: Un Siglo de Historia (Vol. II) (translated: Tanks and Chain Vehicles of the Spanish Army: A Century of History (Vol. II)), Quirón Ediciones, Valladolid, 2005

Donald W Boose Jr, US Army Forces in the
Korean War 1950 – 53, Osprey Publishing, Oxford, 2005

Yuri Pasholok, HMC M37: a Fast Howitzer on a Light Chassis, warspot.net, date viewed 29 January 2024, https://warspot.net/430-hmc-m37-a-fast-howitzer-on-a-light-chassis
Chris Conners, 105mm Howitzer Motor Carriage M37, American Fighting Vehicle Database, date viewed 26 January 2024, http://afvdb.50megs.com/usa/105mmhmcm37.html
Rickard, J (1 August 2014), M37 105mm Howitzer Motor Carriage, date viewed 26 January 2024 http://www.historyofwar.org/articles/weapons_M37_105mm_HMC.html
Matthew J. Seelinger, Tabulated Data – M37 HMC, date viewed 26 January 2024, http://www.m24chaffee.com/m37-105mm-hmc–information.html

Ryabov Kirill, T38 self-propelled mortar project (USA), en.warspot.ru, date 29 January 2024, https://en.topwar.ru/88318-proekt-samohodnogo-minometa-t38-ssha.html
Ryabov Kirill, Early American SAU projects with recoilless guns, topwar.ru, date viewed 29 January 2024 https://en.topwar.ru/88520-rannie-amerikanskie-proekty-sau-s-bezotkatnymi-orudiyami.html

Matthew J. Seelinger, M37 105mm Howitzer Motor Carriages that have survived war, scrap drives, or the gunnery range. , date viewed 26 January 2024, https://www.m24chaffee.com/m37-survivors—restored—unrestored.html
Ryan Soldat, Surviving M37 Howitzer Motor Carriers, date viewed 26 January 2024, http://the.shadock.free.fr/Surviving_M37_HMC.pdf

Walter Elkins, 2nd Armored Division [in Germany], usarmygermany.com, date viewed 7 February 2024
https://www.usarmygermany.com/Sont.htm
Walter Elkins, Field Artillery in the European Theater, usarmygermany.com, date viewed 7 February 2024
https://www.usarmygermany.com/Sont.htm

WW2 US SPAAGs

Combination Gun Motor Carriage M15 and M15A1

Post author By Joshua Allen
Post date June 29, 2024
No Comments on Combination Gun Motor Carriage M15 and M15A1

Combination Gun Motor Carriage M15. Illustration by Oussama Mohamed 'Godzilla', funded by our Patreon campaign.

United States of America (1943-1953)
Anti-Aircraft Half-Track – 2,252 Built

Introduction

The German invasions of Poland and France highlighted a critical need within the US military for a mobile ground anti-aircraft platform. Despite initial disagreement regarding the vehicle’s stability and accuracy, subsequent modifications and recommendations paved the way for the evolution of the anti-aircraft platform. The introduction of the M15 and its variants, such as the M15A1, marked an advancement in American aerial defense capabilities, with production commencing in response to the pressing needs of the North African theater. Throughout its service, spanning from the battlefields of Europe to the Pacific Islands, the M15 and its successors stood as formidable guardians against aerial threats, demonstrating adaptability and resilience in the face of evolving wartime challenges.

The third M15 Combination Gun Motor Carriage built by the Autocar Company. Image source: https://www.usautoindustryworldwartwo.com/autocar.htm

Context and Development

During the German invasions of Poland and France, aircraft caused heavy ground vehicle losses. For the US military, this demonstrated a need for a mobile ground anti-aircraft platform. Using the experience of placing machine gun mounts on trucks, Ordnance decided to place some recently developed machine gun mounts on wheeled chassis to allow for greater mobility. In October 1940, the Ordnance Committee initiated the start of many half-track anti-aircraft projects. These half-tracks used mounts which could rotate 360° with an elevation of at least -5° to 80°, initially using two 12.7 mm (0.5) machine guns. This led to the T1E4, later standardized as the M13 Multiple Gun Motor Carriage (MGMC) and M14 MGMC, which started production around December 1942.

Image Source: https://www.quartermastersection.com/american/afvs/194/M13MGMC

A M13 Multiple Gun Motor Carriage (top) and a M14 Multiple Gun Motor Carriage (bottom). Image Source: http://afvdb.50megs.com/usa/pics/mgmcm14/mgmcm14.html

After a request from the Commander of the Coastal Artillery Board, who was in charge of anti-aircraft weapons at the time, the creation of four new experimental gun motor carriages, based on the M2 Half-track, which were equipped with a 37 mm gun and two 12.7 mm (0.5 in) machine guns, was initiated. These were created in September 1941. In October, they were transported to Aberdeen Proving Ground and received the designation T28 from ‘OCM 17313’ (Ordnance Council Minutes, which was the way the Ordnance Council issued orders, recommendations, and directives). Two of these vehicles, serial numbers ‘1875’ and ‘1862’, had a rotating platform, with the latter having a shield around the gun. Vehicles ‘1858’ and ‘1874’ did not have a rotating platform. These vehicles were armed with the 37 mm M1A2 gun and two water-cooled M2 machine guns, although some initial models (serial numbers ‘1875’ and ‘1862’) lacked the M2 machine guns.

Testing at Aberdeen Proving Ground revealed that the vehicle had adequate gun stability, bullet dispersion, and tracking characteristics of the mount. These tests revealed that there was limited space on the rear of the chassis, which resulted in the recommendation to use the M3 Half-track. The Coast Artillery Board disagreed with the conclusions of Aberdeen Proving Ground after their own test, with their conclusion being that the vehicle was unstable and thus was inaccurate and was canceled in April 1942. This resulted in a recommendation for an MGMC with four 12.7 mm (0.5 in) machine guns. This would later result in the M16 which, apart from having two extra machine guns, was otherwise very similar to the M13.

Image Source: http://www.wardrawings.be/WW2/Files/1-Vehicles/Allies/1-USA/08-Halftracks/File/6-CGMC.htm

A side view of the T28 (top) and a presentation of the T28 MGMC with a gun shield in Washington DC in October 1941 (bottom). Image Source: Scout-cars & Half-tracks J. M. Boniface and J. G. Jeudy

At the same time, American observers with the British Eighth Army in North Africa reported a requirement for a multipurpose anti-tank and anti-aircraft weapon. The recommendation to use a 37 mm gun and 12.7 mm (0.5 in) machine guns, the main US anti-tank and anti-aircraft guns of the early war period, came from former 2nd Armored Division’s commander, Major General Charles L Scott.

A T28E1. Notice the water jackets on the M2 12.7 mm machine guns and the lack of a gun shield surrounding the M3E1 gun carriage. Image source: http://afvdb.50megs.com/usa/pics/mgmct28e1/t28e1lf884.jpg

During July 1942, the Services of Supply, at the request of Armored Force, issued a memorandum to obtain 80 improved self-propelled 37 mm guns to be used in an anti-aircraft and anti-ground role to be used in a special mission. To accomplish this, the Ordnance Board issued ‘OCM 18477’ to create 80 vehicles using the M3 Half-track as a base. These had the troop compartment’s sides and rear armor removed and a mount placed centrally. They would receive the designation Motor, Carriage, Combination Gun T28E1. Production of these began by Autocar in July 1942 and lasted till August.

This T28E1 Combination Gun Motor Carriage was captured by German troops in North Africa and was used during February or March 1943. It is towing a 1 ton (907 kg) “Ben Hur” cargo trailer, with the crew’s positions visible. Image source: № 6010 – US WW2 Half-Track

The 78 T28E1s, with the remaining two kept to facilitate experiments, were issued to the 443rd Anti-Aircraft Artillery (AAA) Battalion in September 1942. These were split into four batteries of 20 vehicles, with the fourth company, D Company, receiving two towed 40 mm guns to give it 20 guns. The T28E1s were actively deployed in the Tunisian Campaign during 1942 and 1943, where they shot down around 78 planes, mostly Ju-87 Stuka dive bombers. Following the end of the campaign and the war in North Africa, they were deployed alongside M15 CGMCs until the end of the war, with vehicles being replaced by M15s when necessary.

A T28E1 of 443rd AAA Battalion guarding the St Raphael airfield in Southern France on 17th August 1944. This shows the gun platform and how the ammunition boxes were stowed. Image source: https://www.militaryimages.net/media/4260.101418/

After an examination by the Anti-Aircraft Artillery Board, the original T28 and the T54, a half-track armed with a 40 mm gun, were deemed unsatisfactory. Nevertheless, the T28 was considered to be more advanced. As a result, the Board decided that the T28 would be useful as an expedient weapon (an expedient weapon was an improvised device, sometimes created by soldiers in the field) if it was modified mainly by using the M3 Half-track and the air-cooled, heavy barrel version of the 12.7 (0.5 in) machine gun using an improved firing mechanism. The other changes, mainly in ergonomics and protection, included:

larger hand wheels
moving the vertical and lead setters’ hand wheels
improving the boresighting equipment
extending the depression to -5°
a mechanism to collect and dispose of empty cases

‘OCM 19087’ of 29 October 1942 incorporated these changes and designated the vehicle as the Carriage, Motor, Combination Gun, M15, and it was recommended to be classed as a Substitute Standard, a piece of equipment used to fill a role temporarily until better equipment was available.

The recommendation for the M15 to be classified as a Substitute Standard gained approval during November 1942, with production being approved to meet requirements for such vehicles in North Africa. The M15 pilot vehicle was manufactured at the Autocar Company, with its evaluation taking place from December 1942 to January 1943 at Aberdeen Proving Ground. This resulted in the gun shield being removed to increase visibility and the amount of 37 mm ammunition to be increased from 140 to 240 rounds. Production lasted from February to April 1943.

An M15 CGMC showing the gun shield and the changed M2 machine guns. Image Source: Standard Nomenclature List G-102

After the T28E1 and M15 were successfully employed in North Africa, demonstrating to the US that there was a need for more M15s. However, the M3E1 gun carriage that the M42 mount was based on was no longer available. To remedy this, it was decided to adapt the M3A1 gun carriage, of which 1,750 were available, combined with the M6 sighting system that created the combination gun mount T87. ‘OCM 21226’ designated this M3A1 gun carriage-based vehicle as the M15E1.

On 12 August 1943, ‘OCM 21281’ standardized the new vehicle as the Carriage, Motor, Combination Gun, M15A1, with this being approved in September 1943. The main changes were using the M54 combination gun mount that located the M2 machine guns below the 37 mm M1A2 and decreased the amount of ammunition carried.

An M15A1 CGMC in the Fort Lewis Military Museum, Washington. Image source: https://en.wikipedia.org/wiki/File:M-15A1_Combination_Gun_Motor_Carriage.jpg

In October 1943, the production of the M15A1 began, lasting until February 1944, with 1,652 M15A1 produced. However, as production was ending, on 24 February 1944, ‘OCM 23270’ was issued, recommending standardizing the M14 computing site for use on the M15A1.

On paper, the end of the M15A1 service began on 12 July 1945, after a recommendation for the M15A1 to be reclassified as a Substitute Standard, which was approved in August 1945. However, the M15A1 would continue to serve until the Korean War, during which it finally left service.

Design

General Dimensions

The M15 CGMC’s total combat weight was 9.1 tonnes (10 tons), with a tyre ground pressure of 2.35 kg/cm2 (33.5 psi). The full-length was 6 m (236.5”), width 2.5 m (98”), height 2.64 m (104”), wheelbase 3.442 m (135.5”), front tread 1.64 m (64,5”), rear tread 1.62 m (98”), and ground clearance 28.4 cm. The pintel height was 71 cm (28”).

An M15 CGMC of the 45th Division in Hampton Roads, Virginia, on 27 May 1943. Image source: https://commons.wikimedia.org/wiki/Combination_Gun_Motor_Carriage_M15#/media/File:MGMC-M15-19430527.jpg