Saturday 14 September 2019

Gorilla, King Kong's Sister

Like other members of the Light Combat Team based on the M24 Chaffee chassis, the 155 mm Howitzer Motor Carriage M41 did not take part in WWII, but fought actively in Korea. Even though the Gorilla was not numerous and its career was short, this vehicle still deserves attention.

In August of 1941 the US Ordnance Committee approved the development of an SPG on the chassis of the Light Tank M3. The development process took longer than a year. As a result, the Cadillac company (a division of General Motors) received a contract for two T16 prototypes armed with the 114 mm (4.5 inch) M1 gun.

A modified Light Tank M5 served as the chassis. The tank was lengthened by 305 mm and a bogey was added on each side. The width was also increased. The power plant, a pair of 110 hp engines, was moved from the rear to the middle of the vehicle, right behind the driver's compartment. The gun was placed in the back without any armour protection. The layout of the T16 was similar to that of the larger M12. This was optimal for a large caliber SPG. A lack of armoured fighting compartment was not critical, since these SPGs were not designed to fire directly, and the rear gun mount reduced the length of the vehicle and allowed ammunition to be loaded from the ground easily.

Both prototypes were ready by the end of 1942, but only one was equipped with the planned armament. The second, the T64, was armed with a 155 mm M1 howitzer. A replacement of the gun was not an issue, since the 114 mm gun had many parts in common with it, but the ammunition capacity was reduced from only 26 rounds on the T16 to 18 on the T64. The T22 ammunition carrier , which used the same lengthened chassis as the SPGs, was designed to carry ammunition for both vehicles.

HMC T64 prototype.

Both prototypes arrived for trials at the Aberdeen Proving Grounds in January of 1943. In February the T16 and T64 were sent to Fort Bragg where they were tested by representatives of the Field Artillery Bureau. Trials were generally successful, although certain issues were discovered. The artillerymen suggested that the ventilation in the driver's compartment needs to be improved, the suspension needs to be reinforced, and the racks on the front of the vehicle need to be reworked. On the T64 they could be damaged by the blast from firing the gun, whose barrel was shorter than on the 114 mm gun. Both vehicles went through trials with the Armor Board in Fort Knox. Overall the results were positive, but it was not meant to be. Neither the T16 nor the T64 made it into production.

A new chassis

A decision was made in April of 1943 to develop a 114 mm SPG and 155 mm SPH on the chassis of the prospective Light Tank T24. The vehicles on this chassis were indexed T16E1 and T64E1, but the first was never built in metal. The 114 mm gun was deemed unsuitable in the field artillery role. Its round was less powerful than that of the 105 mm howitzer. Experience in North Africa showed that three systems were necessary for heavy artillery tasks: the 105 mm howitzer, 155 mm howitzer, and 155 mm gun. As a result only 416 114 mm guns were built and development of SPGs using them ended in February of 1944. The T22E1 ammunition carrier on the T24 chassis was also cancelled then.

HMC T64E1 prototype.

The contract to produce a T64E1 prototype was signed with the Cadillac company only in May of 1944, even though this was approved as early as January 20th. The program was not a high priority one. Production of a prototype took half a year. The T64E1 finally arrived at the Aberdeen Proving Grounds in December of 1944 for the first round of trials. Trials continued in January of 1945 in Fort Bragg. The changes to the design as a result of these trials were minimal. The ammunition rack was changed somewhat and the radio antenna was moved from a bustle to the roof of the engine compartment. The SPG was standardized on June 28th, 1945, as the 155 mm Howitzer Motor Carriage M41.

HMC T64E1 prototype from the rear.

Like other member of the Light Combat Team, the M41 used a slightly lengthened chassis of the Light Tank M24 with the same number of road wheels. The layout was the same as the T64: the engine was moved to the middle and the fighting compartment was in the rear. The armour thickness was up to 13 mm. Unlike the T64, where the gun was completely open, the M41's gun was partially protected from the front and the sides, but the thickness of the superstructure was only 6.5 mm.

HMC M41 in travel position.

The M41 was armed with the 155 mm M1 L/24.5 howitzer. The gun had separate propellant loading with 7 different charges. The main types of ammunition were the M102 (43.13 kg) and M107 (43 kg) HE rounds. There were also several types of smoke rounds and the M118 flare. The M110 chemical shell filled with mustard gas was also developed but never used. The maximum muzzle velocity of the M107 shell was 564 m/s, giving a maximum range of 14,600 m.

Cutaway diagram of the M41.

The gun was installed on a special mount that was built as one unit with the ammunition rack. This made the design lighter. The range of fire was from -5 to +45 degrees vertically (the T64 had 0 to +40 degrees), 17.5 degrees to the right and 20 degrees to the left. The practical rate of fire was up to 4 RPM. The M41 had no auxiliary armament.

A trail with a hydraulic drive was installed in the rear of the SPG. When deployed it formed a convenient workspace for the crew with access to the ammunition rack, which fit 22 rounds.

The M41 was equipped with either the SCR 508 or SCR 528 radio and BC 606 intercom.

The SPG was accompanied by the T41 munitions carrier (standardized as the M39) based on the chassis of the M18 Hellcat tank destroyer. The M41's crew consisted of 12 men, only 4 of which were located on the vehicle while driving. The rest were carried in the M39.

Production and service

The Massey Harris company received an order for 250 M41s in May of 1945. Like with the light tank it was based on and other members of the Light Combat Team, production was reduced with the end of the war. Various sources state that either 60 or 85 SPGs were produces. The former is likely the number produced before the end of WWII and the latter is total production.

The Gorilla (this nickname was given to the vehicle due to the visual similarity with the M12 King Kong) replaced the 105 mm HMC M7 in several armoured divisions. The M41s were organized into battalions of three batteries of 6 guns each. Unlike units that used the M7 and M37s, which had their ammunition carried by trucks, the Gorillas also came with armoured M39 munitions carriers, one per SPG.

Like many other vehicles that didn't make it in time to have a baptism by fire in WWII, the M41 first saw battle in Korea. This war was the only one that the Gorillas fought in.

Crew from the 999th Battalion and their M41.

Two battalions of M41s arrived in Korea: the 92nd and 999th. The latter was "coloured", as the US Army still segregated its troops by race at this point. In November of 1951 the battalion was desegregated.

The 999th Battalion arrived in Korea in August of 1950 as a part of the 3rd Infantry Division. This unit was different from standard infantry divisions as its artillery was self propelled. In addition to the 999th Battalion it had the 58th Battalion armed with 105 mm M37s. At the start of the war the 3rd Infantry Division acted as a "firefighter", covering the retreat of UN forces and the evacuation of civilians. The 999th Battalion was transferred from the division to the 1st Army Corps in early 1951 and replaced with towed 155 mm guns.

The 92nd Battalion was extracted from the 2nd Armored Division (only infantry divisions saw action in Korea) and used as a standard field artillery unit. It spent most of the war in the 9th Army Corps.

The commander of the 9th Army Corps, Lieutenant General William Hodge, preparing to fire the 75,000th shot made by his corps in Korea from one of the 92nd Battalion's SPGs.

M41 from C battery of the 92nd Battalion in position between Hongcheon and Chungheon, March 1951.

The 999th Battalion took part in the battle at the Imjin river in April of 1951. B battery had to leave their positions and break through to their allies. The M39 carriers formed an advance guard, making way for the rest of the battalion with their heavy machineguns. The battalion broke out at the cost of two carriers and five cars lost, two SPGs damaged, 7 KIA and 31 WIA. In another engagement the Chinese managed to capture a couple of intact M41s from the 92nd Battalion. These SPGs were used by their new masters at the battle at Maryang San (October 1951). Presently one of the trophies is on display in Beijing.

Overall the Gorillas showed themselves well. Their chassis was well refined and their armament was powerful. The biggest drawbacks were a lack of protection for the gun and crew and small ammunition capacity. However, given the static nature of the war the latter issue did not have much impact.

A gun from the 999th Battalion firing.

Artillerymen of the 92nd Battalion between battles.

The M41 was not exported with the exception of one vehicle sent to the UK for study. There is information about alleged transfer of some M41s to France, but this information cannot be confirmed. The career of the M41 was not long. The more modern M44s replaced them after the Korean War.


  1. Thank you for writing these articles.

  2. "My Little Sister Can't Be This Cute!"
    - M12 GMC "King Kong"

    ...I regret nothing. >_>