The M18 Hellcat is an American 76-mm self-propelled artillery unit of the tank destroyer class of the Second World War. The light tank destroyer, unlike many self-propelled guns of its time, was built not on the basis of an existing tank, but on a chassis specially created for it. During its production from July 1943 to October 1944, 2507 self-propelled guns of this type left the shops of American enterprises. This tank destroyer compensated for the weak booking with high speed and mobility; when moving on the highway, the self-propelled gun developed a speed of more than 70 km / h.
The path from the beginning of work on the design of a light tank destroyer to a production vehicle, which became one of the most famous American self-propelled guns of the Second World War, contained several experimental samples that were not destined to go into series. Anticipating a possible entry into the war, in 1941 the Americans allocated a lot of funds to re-equip the army. Since the hostilities were planned to be conducted far from the American borders, the Airborne Forces and the Marines were re-equipped first of all. And what have the paratroopers always lacked? Of course, tanks. All countries that at that time had airborne troops were working to provide them with some kind of armored vehicles. The United States did not stand aside, the industry was given an order to create a T9 light airborne tank.
The order for the development of an airborne tank in May 1941 was received by the Marmon-Herrington Company. A full-size mock-up of the novelty, designated Light Tank T9, was ready in August. Further development of the project led to the creation of the M22 airborne tank, which also went down in history under the British designation Locust. It was the only specially designed airborne tank that was used for its intended purpose during the Second World War.
Light Tank T9 prototype
After the project of a light airborne tank was completed, in October 1941, the American military received an offer from Marmon-Herrington to create an anti-tank self-propelled gun based on it. At the same time, the military tried for a long time to understand what is the difference between the tank destroyer project, armed with the same cannon as on the Light Tank T9, installed in a similar turret. As a result, the representatives of the Airborne Forces did not appreciate the peculiar humor and refused the anti-tank tank destroyer based on the airborne tank.
On this, the story of the not even planned self-propelled gun Hellcat could come to an end, but the case helped. The American ground forces were interested in a light, highly mobile anti-tank self-propelled gun. All projects and attempts to create such a machine ended in nothing, and then an airborne self-propelled gun appeared on the horizon. At the same time, in the fall of 1941, the program for the creation of the 37 mm Gun Motor Carriage T42 light tank destroyer was launched, the draft design of which was ready on October 27. The initial concept of this vehicle was not much different from the airborne tank. The main difference was in the more spacious open top turret, which contained the same 37 mm M-5 cannon and a 7.62 mm Browning M1919 machine gun paired with it. On December 8, 1941, the Ordnance Department published recommendations for a tank destroyer that would have a high speed, Christie's suspension and a 37mm cannon.
It is worth noting that for 1941, the 37-mm gun was still at least enough to fight most of the enemy tanks. The Americans did not yet know that German designers were working on the creation of tanks with thick anti-cannon armor. Since the self-propelled gun was no longer supposed to be airborne, its weight and dimensions increased during the design process. By January 1942, the project as a whole was fully completed. The order for the creation of the first two prototypes was placed not with Marmon-Herrington, which still could not assemble the first T9s, but with the large General Motors Corporation (GMC). The General Motors Buick Division received the order for the production of two pilot tank destroyers. At that time, Buick completely stopped producing cars, concentrating exclusively on military orders, the main production of the company was reoriented to the production of aircraft engines.
37 mm Gun Motor Carriage T42 as of late 1941. warspot.ru, Yuri Pasholok
The frontal armor (forehead of the hull and turret) of the T42 GMC tank destroyer did not exceed 22 mm, the sides and stern were covered with armor plates only 9.5 mm thick. Such thin armor was the price to pay for the vehicle's high maneuverability and speed. At the same time, the mass that had grown in the dimensions of the self-propelled gun would most likely have exceeded the mass of the amphibious Light Tank T9, which was about 7.5 tons. It was planned to install the Wright-Continental R-975 engine, which developed a power of 300 hp, which provided the car with a fantastic power density.
No sooner had Buick started producing the T42 GMC when the Artillery Department decided to make changes to the project. In the spring of 1942, taking into account the analysis of the military operations of the British army in North Africa, the American military came to the conclusion that the 37-mm gun was no longer enough to arm tanks and, moreover, tank destroyers. Therefore, they decided to install a more powerful 57-mm anti-tank gun on the SPG. The well-known English "6-pounder" - QF 6 pounder was planned to be installed on the self-propelled gun. Her baptism of fire took place just in April 1942 in North Africa. In the US Army, it was adopted in a slightly modified form, receiving the designation 57 mm Gun M1.
Already on April 18, 1942, an agreement was reached on the creation of two prototypes of new tank destroyers, designated 57 mm Gun Motor Carriage T49. Like their predecessors, they had to be distinguished by excellent mobility and with a mass of about 12 tons, they could reach speeds of up to 55 mph (about 90 km / h). The ACS crew was supposed to be 5 people. The armor of the turret, hull forehead and sides was supposed to be 7/8 "(22 mm), the bottom and roof of the hull - 3/8" (9, 5 mm).
QF 6 pounder
At the same time, the self-propelled gun project has undergone significant changes. If the maximum length of the design T42 GMC was 4715 mm, then the T49 GMC increased to 5280 mm. At the same time, the increase in the length of the hull also led to an increase in the number of road wheels - from four to five per side. The tower for the new self-propelled gun was developed from scratch and was closed. And the body, by its design, turned out to be a completely new development. Even the suspension has undergone significant changes. It was still based on the Christie system, but the candles (coil coil springs) were brought out. This design solution allowed to partially get rid of one of the main problems of Christie's suspension - a large useful volume, which was occupied by the "candles" in the tank hull.
By mid-1942, the first two prototypes of the T49 GMC tank destroyer were ready. In July, these vehicles began testing at a special test site in Aberdeen. The combat weight of the vehicle increased to 14.4 tons. At the same time, a pair of two 8-cylinder Buick Series 60 engines with a volume of 5, 24 liters each was installed on it. Their total power was 330 hp. It is worth noting that these motors have already been installed on passenger cars and were well mastered by the American industry, so there would be no problems with the launch of the T49 GMC with engines.
Already during the tests, it was found that the self-propelled gun cannot reach the declared speed of 55 mph. On tests, the prototype accelerated to 38 mph (about 61 km / h), which was still an excellent indicator for armored vehicles of that time. At the same time, the problem was not in the mass of the combat vehicle and the engines installed on the ACS, but in the torque converter, in which there was a significant loss of power. In principle, the problem with the drop in power was solvable; in the future, it was planned to install a hydraulic transmission on the ACS. An even simpler solution was to find more powerful engines. Despite the fact that it was not possible to achieve the specified speed characteristics, the T49 GMC tank destroyer showed itself excellently when driving over rough terrain. The suspension behaved very well and the tracks had no tendency to fly off even when driving at high speed. Tests have shown that the ACS looks good enough and promising.
T49 GMC
T49 GMC
But this sample did not go into mass production either. Even during the tests, the American military once again thought about replacing the main weapon and strengthening the armament of the vehicle. In the end, this was the reason that work on the T49 GMC project was curtailed. The new target was the installation on the tank destroyer of the 75 mm M3 cannon, which was specially created for the American M4 Sherman medium tank. The difference in armor penetration with the 57 mm Gun M1 was minimal, which could not be said about the power of the 75 mm ammunition. So the next project was born, which received the designation 75 mm Gun Motor Carriage T67.
To accommodate the new 75-mm cannon on the T67 GMC, it was decided to borrow an open round turret from the T35 GMC (a prototype of the future M10 ACS). At the same time, the frontal part of the hull underwent minor changes, the course machine gun disappeared from there, and the armor of the hull's forehead was brought to an inch (25, 4 mm), while the bottom and top of the hull, as well as the sides and stern of the self-propelled gun, on the other hand, were made thinner. Since the turret was open, a large-caliber 12, 7-mm Browning M2 machine gun could be safely placed on top. The first sample of the T67 GMC was ready in November 1942.
In the same month, the new tank destroyer began a series of tests at the Aberdeen Proving Ground. Despite the slightly increased weight, the new self-propelled gun demonstrated approximately the same running characteristics. The fire tests were also successful. The chassis, which had been previously created with a reserve, made it possible to place a new 75-mm gun on it without any problems. The firing carried out showed satisfactory values for the accuracy of the fire. At the same time, according to the test results, it was decided to switch to a torsion bar suspension, and it was also planned to replace the power plant with a more powerful engine. From a pair of two Buicks with a capacity of 330 hp. were going to give up in favor of a 9-cylinder 400 hp air-cooled carburetor engine, which eventually appeared on the M18 Hellcat light tank destroyer.
T67 GMC
Upon completion of the tests at the Aberdeen Proving Ground, the T67 GMC self-propelled gun was recommended for standardization, but the military intervened again. This time, they asked to replace the 75 mm M3 gun (40 caliber length) with a new 76 mm long tank M1 tank gun (55 caliber barrel length) with anti-aircraft gun ballistics. The gun had the best armor-piercing characteristics, which was undoubtedly one of the most important values for a tank destroyer. The T67 GMC chassis, as shown by the tests carried out, should have allowed this gun to be installed. It is possible that the T67 GMC with the new 76mm gun could go into mass production with minor changes, but this did not happen. Another 76 mm Gun Motor Carriage T70 tank destroyer entered the scene.
The concept of the tank destroyer remained unchanged, but the technical implementation of the T70 GMC was completely different. The order for the production of the first 6 pilot self-propelled guns of the new modification was received in January 1943. The first prototype was assembled in the spring of the same year. On the new combat vehicle, instead of a pair of two Buick engines, a radial Continental R-975-C1 was installed, developing a power of 400 hp. To achieve better balance, the 900T Torqmatic drivetrain was moved forward, and the Christie suspension was abandoned in favor of individual torsion bars. The original decision of the American designers was the installation of the engine and transmission on special guide rails, along which they could easily roll out in case of repair or dismantling for replacement. The turret and hull of the new tank destroyer was assembled from rolled homogeneous armor, the forehead of the turret was cast. The armor plates were connected to each other by welding. The 76 mm gun was housed in a welded, open-top turret with ample ammunition space. At the top of the turret was a large-caliber 12, 7 mm M2 machine gun.
T70 GMC
The maximum armor of the hull's forehead was 38 mm, while most of the projections of the ACS had a booking of only 13 mm. The forehead of the turret received 25 mm armor. The ammunition load of the 76-mm M1 gun consisted of 45 rounds. The combat weight of the self-propelled gun reached 17, 7 tons, which, together with the 400-horsepower engine, still allowed to provide outstanding speed characteristics, the Hellcat easily accelerated to a speed of 70 km / h, and the crews compared driving a self-propelled gun with driving a racing car. The open tower had both its clear pros and cons. The pluses included improved visibility, which greatly simplified the task of observing the enemy during the battle. But at the same time, the crew of the self-propelled gun was very vulnerable to mortar and artillery fire of the enemy, as well as from his infantry in close combat. All this, combined with weak armor, which did not allow supporting the advancing infantry, made the M18 a very highly specialized vehicle, which was supposed to hunt enemy tanks from ambush, if necessary, very quickly change its position.
It is worth noting that the T70 GMC anti-tank self-propelled gun, which appeared as a result of serious alterations, which was eventually adopted under the designation M18 GMC aka Hellcat, was in many ways a completely different machine. The hull, turret, engine, suspension, a new transmission that migrated forward - all this has undergone changes and took away from American designers time, which during the war is especially expensive and is often paid for in human lives on the battlefield. When the conceptually the same T67 GMC tank destroyer was launched into mass production with the replacement of the 75-mm cannon with a 76-mm gun, it would be possible to save up to six months. The first T70 GMCs passed combat trials in Italy only at the end of 1943. And in February 1944 they were standardized under the designation M18 Gun Motor Carriage.
M18 Hellcat
