M7, M7B1, M782, Sexton and T57
Type :self-propelled howitzer.
Crew :7 men.
Armament :a 105 mm M2 howitzer; a .50 M2 anti-aircraft machine gun.
Shielding
minimum 12.7mm
maximum 114.3mm.
Dimensions:
length :6.02 m;
width :2.87 m;
height: 2.92 m.
Weight in combat order :23 t.
Ground pressure: 0.73 kg/cm2.
Specific power :15 ch/t.
Engine: Continental R-975 9 cyl. air-cooled gasoline radials, developing 340 hp at 2,400 rpm.
Performance:
road speed: 42 km/h;
off-road speed: 24 km/h;
range on the road: 200km;
vertical obstacle :0.61m;
straight cut: 2.29 m;
ford :1.22 m;
slope :60%.
Service time: introduced in 1942, the machine was used intensively during the Second World War. Used after the war by many armies
American doctrine in self-propelled artillery and the attempts already made to mount the 75 mm howitzer on a light tank chassis led in June 1941 to studies of a self-propelled version of the 105 mm field howitzer that it was proposed to mount on the chassis of the M3 medium tank, then in production. There was no doubt that this chassis and that of the M4, which differed from it only in points of detail, lent themselves best to any further research and on the other hand were not about to be missed. Two pilot models of the new vehicle were therefore built and designated T32 105 mm Howitzer Motor Cardage. The T32 housed the M1A2 field howitzer (on its standard mount) in a tall open superstructure fitted to the M3 chassis. The tests at the Aberdeen polygon brought to light all the promises of the T32; in fact the only major criticism was the lack of an anti-aircraft weapon. A circular mount for a .50 machine gun was therefore added to the front right corner of the superstructure. Once streamlined and armoured, this lookout, which became a cupola, looked like a church pulpit; hence the nickname "Priest", which soon became inseparable from the vehicle. Some 600 T32s were ordered in February 1942 and the vehicle was standardized in April of the same year, under the designation of M7 105 mm Howitzer Motor Carnage. The manufacture of Priest was entrusted to the American Locomotive Company (Alco) and started on the chassis of the tank ma When the production of this last machine ceased, in December 1942, the manufacturers realized that the hull of the medium tank M4A3 would be very suitable well at the Priest and the new machine took over the assembly lines.
Priests, derived from the M4A3 and equipped with the Ford GAA engine, received the designation of M7B1. Subsequently, some slight modifications to the upper section of the superstructure raised the "pulpit" a little and brought the designation of M7B2. The standard 105 mm howitzer fired a breaker at a range of 10.973 km and could employ many other types of ammunition, including smoke or chemical shells. In the British Army, the equivalent of the 105 mm howitzer was the 25-pounder, so a very similar conversion was made on the M3 chassis; the craft was 25-pounder and was given the name Sexton. Allowing the British to keep their 25-pounders while leaving their 105mm to the Americans had an undeniable logistical advantage:the 105mm ammunition was reserved for the American army while the 25-pounder was standardized in the 21st Group of armies. The Sexton was therefore produced in large quantities for the army of His British Majesty and those of the Commonwealth. A compromise vehicle, the T51 25 Pounder Gun Motor Carnage, was produced in July 1942 but disappeared when it was realized that no one needed it. The Priest was the first valid self-propelled on Allied materiel rolls and as early as 1942 the British Purchasing Commission in the United States requested delivery of 5,500 units by the end of 1943. The order was never to be fully executed but the production started very quickly and in September 1942, the VIIIth Army could align 90 machines. In El Alamein, in November, Priests of the 5th Regiment Royal Horse Artillery, wanting to cover British tanks, launched a charge against powerfully entrenched 88 guns.
The American Locomotive Company released 3,314 M7s, and Pressed Steel 826 (of which 450 were M7B1s). The Federal Machine and Welder Company produced 127 M7B2s, bringing the total to 4,267. Great Britain served in Italy and Normandy. Most were replaced by Sextons and then converted into observation post vehicles and Kangaroo armored personnel carriers, where the howitzer disappeared leaving enough space for up to twenty infantrymen.