Work on the creation of a promising self-propelled gun with a caliber 105 mm started in July 1943 year. Initially, several variants of the combat vehicle were considered, which included the use of different basic chassis. It quickly became clear that the new SAU should not be built on the basis of the M4 Sherman medium tank. This chassis was too large and heavy for a relatively light 105-mm howitzer. The lightweight tank M24 Chaffee was considered a more convenient option for the base chassis. Using its chassis would allow to successfully solve all the tasks set without special technical and technological problems. In addition, this choice of base machine allowed the project to include a new self-propelled gun in the program Light Combat Team, whose task was to create a family of armored vehicles based on the latest light tank.
The new project received the working designation T76. As part of this project, it was planned to transfer the basic layout solutions of Priest ACS to a new chassis with minimal changes to the latter. This, in particular, explains the almost complete preservation of the overall layout of the base tank chassis, which has not undergone significant changes. In the case of other projects, self-propelled guns based on the Chaffey tank used groundwork for the M12 project and later armored vehicles: the engine was transferred from the stern to the middle part of the hull, which made it possible to free up a platform for placing the gun. In the T76 project, the base chassis was to keep the stern engine compartment, and the new fighting compartment in the form of a large open top cabin was located in the middle and aft parts of the hull.
The T76 ACS received an armored hull based on the M24 light tank units. Was saved frontal part, consisting of three armor plates. As before, the frontal parts were located at different angles to the vertical. The under-turret box was removed, which made it possible to increase the available volumes to accommodate the combat compartment. The engine was located in the armor cover in the rear part of the vehicle and was connected to the front transmission compartment with a propeller shaft passing through the fighting compartment. Behind the hull front plates, an armored felling began, covering the entire space of the crew compartment and the roof of the engine compartment. In the center of the frontal hull sheet was a gun mount with an armored mask. To the right of her provided a cylindrical unit with the place of the assistant driver and a machine gun turret.
According to reports, despite the preservation of the main parts of the hull, the thickness of the armor plates has changed. Most of the details of self-propelled guns T67 had a thickness of 13 mm. A sufficient level of protection was achieved with rational booking angles. The sheets of the body were connected to each other by welding.
The use of a common layout, borrowed from the M7 Priest project, made it possible to dispense with major reworking of the base chassis. In addition, the composition of the M24 tank units remained the same. At the rear of the hull were two Cadillac 44T24 petrol engines with 110 horsepower each. With the help of a cardan shaft, they were associated with a mechanical transmission in the front of the case. The latter provided eight forward speeds and four rear. Torque engines transmitted to the front drive wheels. In the fuel tanks of the engine compartment was poured 420 liters of fuel.
Chassis borrowed from "Chaffee" unchanged. It consisted of five dual road wheels on board. Individual suspension was based on torsion bars. In addition, all pairs of rollers, with the exception of the third, were equipped with additional shock absorbers, designed to compensate for the load on the chassis. The self-propelled gun could be equipped with two types of tracks, 410 or 360 mm wide (419 mm when using additional elements).
A M5-type gun mount with horizontal and vertical pick-up drives was located in the heading list of the ACS chopping house. With its help, it was possible to direct the gun within the horizontal sector with a width of 25,4 ° to the left of the vehicle axis and 26,3 ° to the right, the corners of the vertical pickup ranged from -10,5 ° to + 42,8 °. Guidance mechanisms were manually actuated.
The main weapons The T76 ACS was supposed to be the M105 4-mm howitzer, which was a modified version of the M1 / 2 field gun (modern designation M101) with some modifications for installation on self-propelled combat vehicles. The howitzer was equipped with a 22 barrel with a caliber and could use projectiles for various purposes. The range of its ammunition included high-explosive, smoke, chemical and other projectiles. The initial velocity of the shells reached 470 m / s, the firing range exceeded 11,1 km.
Due to the relatively large size of the fighting compartment, due to the dimensions of the cabin, the T76 self-propelled gun had a rather large mobile load. On several racks of the fighting compartment, it was possible to place 68 unitary shells of caliber 105 mm, which made it possible not only to fire for a long time, but also to enter into ammunition enough quantity of ammunition of one type or another. Later, in the course of refinement of the test results, the ammunition was increased to 126 shells.
An annular turret T107 was mounted on the left front cylindrical part of the body with attachments for the M2HB large-caliber machine gun. The turret made it possible to fire in any direction with large elevation angles. The ammunition of the machine gun was 990 cartridges. Tapes with them were placed in the styling of the fighting compartment.
As an additional weapon for self-defense, it was possible to use the crew’s personal armament: carbines and submachine guns. Thus, the crew had the opportunity to protect against attacks from the air, and from attacks by enemy manpower.
The crew of a promising self-propelled gun was to consist of seven people. The two, the driver and his assistant, were located in front of the hull. In this case, the driver's seat was below the level of the roof of the case, while the assistant was inside the cylindrical unit. The remaining five crew members, including the commander and the gunner, were located on the ground in the fighting compartment. During the firing they had to perform various tasks for the maintenance of the gun.
The use of ready-made layout solutions allowed to maintain the size and weight of the machine at an acceptable level. The total length of the vehicle was 5,5 m, width - 3 m, height (taking into account the machine gun on the ring turret) - 2,84 m. The combat weight was determined at the level of 21 t. Despite some increase in combat weight in comparison with the M24 Chaffee tank, the main parameters of mobility remained at the same level. The maximum speed on the highway reached 56 km / h, the power reserve was 160 km. Opportunities to overcome obstacles, including shallow fords, generally have not changed.
Due to the workload of enterprises development project T76 noticeably delayed. The first prototype of this combat vehicle was built only in the early summer of the 1944 of the year. In July, trials started at the Aberdeen Proving Ground. The checks were quite successful and did not lead to a serious delay in the work. Serious improvements are not needed, because of what all the necessary work ended by the beginning of the next 1945 year.
In general, the car was considered successful and recommended for adoption. The new self-propelled gun was based on the chassis of the newest light tank and had a rather powerful weapon. Some complaints were caused by relatively weak reservations, but in terms of the aggregate characteristics of ACS T76 was considered quite successful.
By January 1945, all tests and improvements were completed, after which the new armored vehicle was put into service. At the same time, the self-propelled gun received a new army designation M37 Howitzer Motor Carriage. Soon, American Car & Foundry received an order for the supply of 448 production cars of a new type. The fulfillment of this order was associated with some difficulties associated with the need for the massive construction of M24 Chaffee tanks.
Due to the higher priority of the construction of tanks, the production of self-propelled guns faced a lack of basic chassis. As a result, less than a hundred serial self-propelled guns were built by the end of World War II. Soon after the battles were over, it was decided to transfer the order to Cadillac, as well as reduce its volume to 317 machines. However, the contract was not fully executed. After completing the construction of the next party, the military decided to curtail production. A total of 150 self-propelled guns were assembled and shipped.
Because of the start of production in the winter of the 45, the newest self-propelled artillery mounts M37 HMC did not have time to get into World War II. The main machine of this class with an 105-mm gun until the end of the fighting remained M7 Priest, which was already considered obsolete. After the end of the war, the troops continued to master the new ACN systems M37 and used them in various combat training exercises. In the future, this technique got to war.
Like some other models of armored vehicles that appeared at the final stage of World War II, the M37 HMC took part in the hostilities in Korea. During this war, self-propelled guns were used to fire remote targets from closed positions, as well as for direct fire support of troops. At the same time, however, direct fire was not the main task of combat vehicles.
Inside the combat department of the museum ACS. To the left is the breech of the gun, to the right is the engine compartment. Photo Afvdb.50megs.com
Shortly after the end of the Korean War, the gradual withdrawal of the M37 from service began. Artillery units parted with the M37 and received new ACN MXXUMX with a gun of the same caliber. By the end of the fifties, the US ground forces had completed the decommissioning of outdated equipment, both the M52 HMC self-propelled guns and other vehicles based on the M37 Chaffee light tank.
Most of the T76 / M37 self-propelled guns were scrapped as unnecessary, but some vehicles of this type continued to serve in the armed forces of third countries. So, the Spanish army was transferred 36 similar machines, which were in service for quite a long time. The last military line M37 of the Spanish army was written off in the seventies. In addition, a number of self-propelled guns in the late forties and early fifties were given to friendly countries for testing and study.
The vast majority of self-propelled guns M37 HMC after the service went for recycling. Nevertheless, about two dozen armored cars managed to avoid this sad fate. They went not to the smelter, but to museums. This technique is kept in museums in the USA and Spain, and the surviving specimens often differ from each other in their condition. Some of them were repaired and restored in a timely manner, while others are half disassembled machines that need to be restored.
The M37 Howitzer Motor Carriage ACS has become a typical representative of the Light Combat Team family of vehicles built on the basis of the M24 Chaffee light tank. The project turned out quite successful, but its development began too late, because of which the serial self-propelled guns did not have time to get to the Second World War, for which they were created. Later, they, together with other vehicles of their family, continued their service and even took part in the Korean War, after which, however, they were removed from service and decommissioned.
Hunnicutt RT Stuart. A History of the American Light Tank, Volume 1. Navato, CA. Presidio Press, 1992
The list of preserved M37 HMC with photos:
Detailed photo reviews of the M37 ACS: