One of the results of the Second World War was the increased interest of the military of the leading countries in promising anti-tank weapons. The growth in the level of protection of modern armored vehicles increased significantly, which required the appropriate anti-tank weapons. One of the main ways of developing such systems has become recoilless weapons, from light hand grenade launchers to large-caliber guns that require a tractor or self-propelled chassis. In this area, various attempts have been made to create new military equipment based on existing models. So, in 1945, an interesting project was launched in the United States to develop combat vehicles with recoilless weapons based on existing chassis created on the basis of the M24 Chaffee light tank: the M37 HMC self-propelled gun and the M19 MGMC anti-aircraft self-propelled gun.
The first experiments to install recoilless weapons on existing equipment, which became the forerunner of the new program, began in the spring of 1945. The first project of this kind involved a slight modification of the design of the new M37 HMC self-propelled artillery unit, which implied the replacement of auxiliary weapons. In the basic version of this machine, built on the basis of the M24 tank, a T107 ring turret with attachments for the M2HB heavy machine gun was located on the side cylindrical hull unit. Such weapons should have been used against enemy infantry and aircraft. At the beginning of the 45th, a proposal appeared to increase the firepower of self-propelled auxiliary weapons.
ACS M37 HMC with a 75-mm recoilless gun on a machine gun turret
Over the course of several months, some design work, refinement of prototype machines and tests were carried out. Serial M37 self-propelled guns, relatively recently rolled off the assembly line, were taken as the basis for the prototypes. In the course of these work, two vehicles were re-equipped (according to other sources, both times the same self-propelled gun received new weapons). The project involved dismantling the existing machine gun and installing a recoilless gun in its place.
It is known about the testing of two systems of auxiliary weapons. A 75-mm T21 recoilless gun and a 107-mm M4 "recoilless mortar" were mounted on the ACS turret. This weapon was to be used by the assistant driver in conjunction with other crew members. Ammunition was housed in the fighting compartment.
M37 with "recoilless mortar" M4
The details of the tests of such modified self-propelled guns are unknown, however, the available sources note the characteristic disadvantages of the project. The open-top design of the cabin of the base M37 self-propelled guns seriously impeded the use of recoilless weapons, which, when fired, emitted flames and reactive gases. In order to avoid injuries to the crew and damage to the vehicle units, up to the most dire consequences, it was possible to fire from recoilless additional weapons only in certain sectors. At the same time, safe firing sectors were not located in the most convenient way for effective fire.
The use of recoilless guns as a replacement for a machine gun made special demands on the design of the base vehicle. For this reason, improvements to the M37 self-propelled gun were considered impractical and unpromising. Nevertheless, work on the promising program did not stop. Already in the summer of 1945, a new stage began, during which a full-fledged combat vehicle with new weapons was created. This time, it was decided to abandon the idea of re-equipping the existing equipment and create a completely new project based on ready-made components.
An analysis of the possibilities showed that the optimal base for a promising self-propelled gun with anti-tank recoilless weapons is the M19 MGMC anti-aircraft gun, built on the basis of the M24 Chaffee tank and armed with two 40-mm cannons. This choice, first of all, was due to the rather successful layout of the base machine. The M19 chassis had a standard layout for American self-propelled guns of that time. In the front part of the hull there was a control compartment and a compartment with transmission mechanisms, an engine was installed in the center, and the feed was released under the fighting compartment with a shoulder strap for a rotary turret.
First variant of the M19 with a new turret and 75 mm T21 cannons
In the basic configuration, the ZSU M19 was equipped with a four-man open-top rotating turret, which housed two 40-mm automatic cannons. The design of the base chassis and turret provided circular guidance in the horizontal plane. A new experimental project proposed abandoning the existing turret and replacing it with a new combat module with recoilless weapons. According to reports, the new tower was developed on the basis of some of the units of the old one, but differed in many different elements.
In fact, the only surviving element of the tower was the lower platform, installed on the shoulder strap of the hull. It installed onboard armored units of a curved shape, designed to protect the crew and weapons from bullets and shrapnel. At the same time, the right side of the tower had a relatively small width, and its rear part was replaced by a mesh on the frame. The left side, in turn, covered the entire side projection. In the left side, a niche was provided for storing various property.
Modified M19, rear view
In the central part of the new turret, an installation for four recoilless guns was mounted, made on the basis of the existing M12 system. Its design made it possible to direct the armament horizontally by turning the entire turret, and vertical aiming was to be carried out using the appropriate manual mechanisms. The gun mount had a design in which the barrels protruded from the front "window" of the tower, and the breeches had to remain within the combat module, to some extent facilitating reloading.
The assembly of the first prototype of a promising ACS was carried out by specialists from the Aberdeen Proving Ground. The work did not take long: the car was ready for testing in June 1945. Shortly thereafter, she went to the test site.
Initially, it was assumed that the new combat vehicle will receive four recoilless type T19 105 mm guns. However, at the time of construction of the prototype, the specialists did not have the required weapons, which is why the project was slightly modified. The ACS entered trials with a new weapon in the form of four 75 mm T21 guns. Such systems had a smaller caliber and were inferior in their characteristics to those originally planned, but were available and could be used in the assembly of the prototype without any delay.
The last prototype with T19 guns
The aim of the project was to test the possibility of installing recoilless guns on existing tracked chassis and to evaluate the characteristics of such equipment. Due to the absence of major changes in the dimensions or weight of the prototype vehicle in comparison with the base M19, it was possible to do without sea trials and go straight to test firing. Such tests showed the viability of the idea, as well as the acceptable characteristics of the proposed vehicle, even in a "simplified" configuration with 75-mm guns.
The 75 mm T21 recoilless gun reportedly had a 5 ft (1524 mm or 20.3 caliber) barrel and weighed 48.6 pounds (22 kg). The system used cumulative ammunition, similar to those used by early American-designed hand grenade launchers. The warhead of the ammunition made it possible to penetrate up to 63-65 mm of homogeneous armor when fired from a distance of no more than several hundred meters.
According to its characteristics, the T21 gun was not the best representative of its class, although in the case of a promising self-propelled gun project it did an excellent job with the tasks. The principal possibility of installing recoilless systems (including in the form of several guns) on existing and future armored chassis was confirmed. Based on the test results of the first prototype based on the M19 MGMC, it was decided to continue work and build an experimental combat vehicle with 105 mm guns.
He, side view
Autumn and winter of 1945 were spent on creating an updated project. The general layout of the promising ACS remained the same. On the base chassis from the ZSU M19 MGMC, it was proposed to mount a turret of a new design with four 105-mm recoilless guns. This time, the project was created taking into account the possible start of mass production and deliveries to the troops, which affected a number of features of the turret design. The main innovation in this case was the use of full-fledged booking to ensure the required level of crew protection.
The overall layout of the tower has not changed. In the central part of the platform there was a gun mount, on the sides covered by onboard armored units. The design of the latter has been significantly modified to meet the requirements for the level of protection and ergonomics. On the side, the crew and weapons were protected by box-shaped units made of curved sides, as well as straight frontal parts and roofs. No feed sheets were provided. The left unit, for certain reasons, was smaller in comparison with the right one. Along the sides there were places for the crew and mounts for ammunition. The shots were transported in an upright position.
Rear view, large breeches of guns are clearly visible
Four 105 mm T19 recoilless guns were mounted on the central turret mount. It was proposed to charge them one by one, by opening the gates and placing shells from the packs in the chambers. Due to the larger caliber, the T19 guns were significantly superior in range and power to the previously used T21s.
The assembly of a new prototype self-propelled gun based on the ZSU M19 with four T19 guns was completed in the spring of 1946. In April, the car entered the test range and took part in the tests. The details of these tests are unfortunately not known. It can be assumed that in terms of protection, fire and overall combat effectiveness, the updated ACS should have significantly surpassed the prototype of a simplified configuration. In addition, in terms of the main parameters, it fully complied with the previously imposed requirements.
According to reports, no later than the fall of 1946, all work on the creation of self-propelled guns with recoilless weapons on the basis of existing machines of the M24 Chaffee family ceased. Probably the main reason for this was the lack of noticeable prospects for the existing chassis, created during the Second World War. In addition, the fate of these developments could be affected by their experimental nature. The assembly of prototypes made it possible to try out new ideas in practice, without complicating the work of building completely new combat vehicles. After the tests, respectively, the need for such a technique has disappeared.
SPG with T19, top view
In the future, the American defense industry continued to develop recoilless guns and vehicles for them. Thus, the 105-mm T19 gun passed the entire range of tests, after which it was put into service under the designation M27. Such weapons were installed on various platforms, primarily off-road vehicles, and even used during the fighting in Korea. The most interesting representative of the class of self-propelled guns with recoilless weapons was the M50 Ontos combat vehicle, created in the early fifties. A turret with six 106-mm recoilless guns was installed on the basic armored chassis of this vehicle.
American projects of self-propelled artillery installations with recoilless guns, created in the second half of the forties, did not reach the stage of serial production of finished equipment. Moreover, all well-known projects in this area did not even have their own designations. Nevertheless, they allowed us to study an important topic and work out the basic issues of creating such a technique. In the future, developments on unnamed projects were used to create new military equipment, including those that reached the troops.
