T16 4.5in Gun Motor Carriage
The T16 4.5in Gun Motor Carriage was a design for a self-propelled gun that was originally to be carried on a new chassis based on that of the M5 Light Tank, but that was then modified to use the M24 Light Tank chassis, before being cancelled.
Work on the T16 began in May 1941 when the intention was to mount a 4.5in gun on a chassis made from parts of the M3 Light Tank and parts of the newer T7 Light Tank.
The T16 was designed by Cadillac, the producers of the M5 Light Tank. It was developed at the same time as the T18 75mm Howitzer Carriage, T56 3in Gun Motor Carriage and T57 3in Gun Motor Carriage, all attempts to produce a self propelled gun using the standard M3/ M5 chassis. All three projects failed because the small light tank chassis simply didn't have enough space to carry the bigger guns.
Cadillac took a different approach to the problem. They produced a new chassis based on that of the M5, but lengthened by the addition of a third two-wheel bogie on each side of the vehicle. The engine was moved to the centre of the chassis from the rear, leaving space at the back for the gun compartment.
Two pilot models of the T16 were completed by the end of 1942, one with the 4.5in gun and one with a 155mm Howitzer and the new designation T64 155mm Howitzer Motor Carriage. They were tested at the Aberdeen Proving Ground and by the Artillery Test Board and performed well, but in April 1943 work began on a new light tank, the T24 (later to enter service as the M24 Chaffee). The new tank was being designed with alternative uses in mind, and the Artillery Test Board recommended that the T16 should be redesigned to use the new chassis. The T24-based version was given the designation T16E1, but the Armored Board then decided not to use the 4.5in gun and in February 1944 the T16 programme was cancelled.
The new M5 based chassis became the basis of a family of vehicles called the Light Combat Team. The idea was to simplify maintenance by using a common chassis for a variety of gun carriages. The extended M5 chassis was used as the basis for the T64 155mm Howitzer Motor Carriage, T65 40mm Gun Motor Carriage and T85 20mm Gun Motor Carriage. All of these projects moved onto the M24 chassis, becoming the T64E1 and T65E1. Of these projects the T64E1 entered production as the M41 Howitzer Motor Carriage and the T65E1 as the M19 Multiple Gun Motor Carriage.
During the early stages of World War II, US Army observers realized that they would need a self-propelled artillery vehicle with sufficient firepower to support armored operations. Lessons learned with half-tracks (such as the T19 Howitzer Motor Carriage (HMC) with a 105 mm howitzer on the M3 Half-track chassis) also showed that this vehicle would have to be armored and fully tracked. It was decided to use the M3 Lee chassis as the basis for this new vehicle design, named T32.  The pilot vehicles used the M3 chassis with an open-topped superstructure, mounting an M2A1 105 mm howitzer, with a machine-gun added after trials.
The T32 was accepted for service as the M7 in February 1942 and production began that April. The British Tank Mission had requested 2,500 to be delivered by the end of 1942 and a further 3,000 by the end of 1943, an order which was never fully completed.  
As the M4 Sherman tank replaced the M3, it was decided to continue production using the M4 chassis (the M4 chassis was a development of the M3). The M7 was subsequently supplanted by the M37 HMC (on the "Light Combat Team" chassis that also gave the M24 Chaffee light tank). 
A total of 3,489 M7s and 826 M7B1s were built. They proved to be reliable weapons, continuing to see front-line service in the US and other armies well past the end of World War II.  
North Africa Edit
During the North African campaign, 90 M7s were received by the Eighth Army in North Africa, which was also the first to use it, during the Second Battle of El Alamein, alongside the Bishop, a self-propelled gun based on the 87.6 mm calibre Ordnance QF 25-pounder gun-howitzer. 
The British Commonwealth armies had logistical problems in supplying the M7, as it used US ammunition that was not compatible with standard British artillery pieces or tank guns, and had to be supplied separately.  Whereas the Sexton – a rival self-propelled gun developed in Canada - featured the standard British QF 25-pounder (on an M3 or M4 chassis). 
Despite supply problems, British Commonwealth forces used the M7 throughout the campaigns in North Africa and Italy.
North-West Europe Edit
During the invasion of Normandy, from June 1944, the artillery regiments of the British 3rd and 50th divisions, and the Canadian 3rd Division were equipped with the M7 however, these were replaced by towed 25-pounder guns in early August.  
During the Battle of the Bulge, each US armored division had three battalions of M7s, giving them unparalleled mobile artillery support. 
Pacific War Edit
The M7 was also used by US and British forces in Pacific and Asian theaters.
During the Burma campaign, the Priest played a significant role, in particular, at the Battle of Meiktila and the advance on Rangoon (1945). After the Sexton became available in South East Asia, most British M7s were converted into Kangaroo armored personnel carriers.
From early 1944 it was used in the South West Pacific theater, by the US Sixth Army in the later stages of the campaign in New Guinea and surrounding islands. The M7 also saw action in the Philippines campaign, with the US Eighth and Sixth armies.
After World War II Edit
M7 Priests remained in use during the Korean War, where their flexibility, compared to towed artillery units, led the US Army on the path to converting fully to self-propelled howitzers.  The limited gun elevation of the M7 (35 degrees) hampered its ability to shoot over the tall Korean mountains, so 127 M7B1s were modified to permit the full 65 degrees elevation in a model known as the M7B2. After the Korean War, many of these were exported to NATO countries, notably Italy and Germany. 
Israel acquired a number of M7 Priests during the 1960s and employed them in the Six-Day War, the War of Attrition and the Yom Kippur War. In the last conflict, three M7 units, the 822nd, 827th and 829th Battalions in the IDF Northern Command, supported the occupation of the Golan Heights. 
The new West German Bundeswehr received 127 Priests as its first self-propelled artillery vehicle. They entered service in 1956 and were used until the early 1960s.
One surviving vehicle is now shown at the Deutsches Panzermuseum Munster (German Tank Museum Munster).
A restored vehicle at the Australian Armour and Artillery Museum, in Cairns, features a World War II US Army paint scheme.
Survivor vehicle at Vermont National Guard Library & Museum Colchester, Vermont
A surviving M7B1 and an M7B2 is on display at the Texas Military Forces Museum in Camp Mabry, Austin, Texas.
A surviving M7 which was used in the Austrian Bundesheer (Army) after WWII is exhibited in the private Robert Gill Collection in Austria www.militarymuseum.at [Vienna, Austria]
A British self-propelled gun armed with the Ordnance QF 25-pounder in design from 1941 was nicknamed Bishop as its appearance was said to resemble a bishop's mitre and a replacement, the US 105 mm Howitzer Motor Carriage M7, was called "Priest", as part of its superstructure was said to resemble a pulpit. Following this line of names, a 1942 self-propelled gun armed with the QF 6 pounder was named Deacon and a 1943 weapon carrier with the QF 25-pounder was called Sexton.
In 1920 the US Army Ordnance started to work on a new medium field gun. Since the US Army had already employed the 4.7 inch Gun M1906 during World War I, this caliber was also selected for the new weapon. The development resulted in 4.7 inch Gun M1922E on Carriage M1921E. Due to lack of funding, the design never reached production.  
In 1939 the program was restarted the renewed design, designated 4.7 inch Gun T3, was ready by early 1940 it utilized the same carriage as the concurrently developed 155 mm howitzer. At this stage, the army decided to change the weapon to use the British 4.5 inch ammunition. The modified gun was standardized in April 1941 as 4.5 inch Gun M1 on Carriage M1.  
The production started in September 1942 and continued until February 1944. 
|Production of M1  |
The M13 half-track was 21 feet 4 inches (6.50 m) long, 7 feet 1 inch (2.16 m) wide,  and 7 feet 8 inches (2.34 m) high with a wheelbase of 135.5 inches (3.44 m).  It had bogie suspension for the wheels and vertical volute springs for the tracks. It had a 60 US gal (50 imp gal 230 L) fuel capacity and a range of 175 miles (282 km). The vehicle was powered by a six-cylinder White 160AX, 128 horsepower (95 kW), 386 cubic inches (6,325 cc) gasoline engine, with a compression ratio of 6.3:1. It had a power-to-weight ratio of 15.8 horsepower per short ton (17.7 hp/LT 17.4 hp/t) and weighed nine short tons (8.0 long tons 8.2 t).  The armor across most of the vehicle was 0.25 inches (6.35 mm) thick with a 0.5 inches (12.7 mm) thick windscreen visor. The vehicle was armed with two 0.5 inch M2 Browning heavy machine guns placed on an M33 Maxson mount.    The two machine guns were fired remotely and powered by a small electrical motor near the back of the turret. The guns were aimed with a Mark 9 reflector sight. Each vehicle had a crew of five (commander, driver, gunner, and two ammunition loaders). 
Early experiments Edit
In October 1940, development began to produce a vehicle in response to a long-standing requirement for an anti-aircraft vehicle to protect the U.S. Army's mechanized troop convoys from aerial attack.   The first vehicle produced in the development of a half track with an anti-aircraft armament was the T1, which had two M2 machine guns on a Bendix machine gun mount—as used on jeeps—on a 4×4 truck. The T1E1 had a power-operated Bendix mount, and the T1E2 a Maxson mount. The T1E3 had an electro-dynamic Glenn L. Martin Company aircraft-type turret. Evaluation of these test vehicles led to the T1E2 design being preferred. The T1E2 became the M16 half-track by replacing the M33 with the M45 mount and the M2 half-track chassis with the M3 half-track chassis.     
T1E4 and M13 Edit
The next stage of development was to use the T1E2 configuration on the longer chassis of the M3 half-track, since it could store more ammunition. This vehicle, originally designated as the T1E4, was accepted into production as the M13 Multiple Gun Motor Carriage on 27 July 1942.    A total of 1,103 examples of this variant were produced from 27 July 1942 to 15 May 1943. Half of them (583) were converted into M16s by the White Motor Company before reaching the army. Deliveries began in late 1943.     
Sources & Links about the M18 Hellcat
AFV Data Base
The Pacific War Online
“Seek, Strike, and Destroy: US Army Tank Destroyer Doctrine in World War II.” Dr. Christopher R. Gabel Combat Studies Institute, US Army Command and General Staff College Fort Leavenworth Kansas September 1985
Buick M18 Hellcat Tank Destroyer First Drive – Four Wheeler
M18 76mm Gun Motor Carriage Hellcat – History of War
M18 Gun Motor Carriage (Hellcat) – Tank Destroyer/Gun Motor Carriage – History, Specs and Pictures – Military Factory
UNITED STATES ARMY IN WORLD WAR II, The European Theater of Operations – “THE LORRAINE CAMPAIGN” Hugh M. Cole
The M13 served at the landing at Anzio with the VI Corps of the Fifth United States Army in January 1944. It was used as an anti-aircraft weapon during the initial landing and then later as a ground support weapon to repel heavy German panzer attacks on the beachhead. It was replaced three months later by the M16 Multiple Gun Motor Carriage in April 1944.     Only 139 examples were deployed overseas by the U.S. Army.  
Ten were transferred to the United Kingdom under Lend-Lease. 
M40 Gun Motor Carriage
The 155 mm Gun Motor Carriage M40 was a US self-propelled artillery vehicle built on a widened and lengthened Medium Tank M4A3 chassis but with Continental engine and with HVSS (Horizontal Volute Spring Suspension) that was introduced at the end of the Second World War. Equipped with a 155 mm M2 gun, it was designed to replace the earlier M12 Gun Motor Carriage. Its prototype designation was the T83, but this was changed to the M40 in March 1945.
A single pilot vehicle was used in the European Theatre in 1945 by 991st Field Artillery Battalion, along with a related 8 inch Howitzer Motor Carriage T89 which was sometimes also equipped with a 155 mm barrel. Ώ] A total of 311 out of a planned 600 were completed before the end of the war. From there it was deployed during the Korean War.
After World War II the M40 was used by the British Army, who designated it '155 mm SP, M40 and called it Cardinal in the tradition of using ecclesiastical names for SP artillery, such as Deacon, Priest, Bishop and Sexton.
Description [ edit | edit source ]
Features [ edit | edit source ]
QF stands for "Quick Firing", a British term for ordnance that fires ammunition with a metal (usually brass) cartridge case containing the propellant charge. The cartridge case also provides obturation, or sealing the chamber. This howitzer was the largest calibre of British QF field artillery ordnance.
Apart from extensive experimentation with shell and rifling designs, two problems slowed development both were howitzer specific issues. The first was the need for an adjustable quick firing recoil system to prevent the breech striking the ground when fired at high elevation angles. The second was the suitable design for a range scale in yards able to accommodate a choice of propelling charges. The first was solved by use of “cut-off-gear” that allowed 40 inches of recoil when the barrel was horizontal but only 20 inches when it was at 45 degrees. The second led to the range scale being designed for charge 4 and a “range rule” provided to convert the actual range for other charges to a false range set on the charge 4 scale.
The gun carriage was designed to be towed behind a limber and 6 horses the lower carriage comprised a box trail. The QF 4.5 fired a separate round (i.e. shell and cartridge were loaded separately). The barrel was of built-up type, with a horizontal sliding block breech. A limited traverse saddle supported the elevating mass and a shield. It was designed for one-man laying with both traverse and elevation controls and sights on the left. The recoil system was below the barrel and used a hydraulic buffer with a hydro-pneumatic recuperator to return the barrel to its firing position.
Originally fitted with rocking bar open sights including a deflection scale and a strip elevation, by 1914 the Number 7 Dial Sight in Carrier Number 7 Dial Sight Number 1 had been introduced. This carrier was reciprocating (i.e. it could be cross-levelled), it had an integral elevation scale drum and a mounting for the sight clinometer (used for the angle of sight). Β] The Number 7 Dial Sight was a modified version of the German Goertz panoramic sight. The only changes to the ordnance, creating the Mark II in 1917, with a reduced twist in the rifling (from 1:15 to 1:20) and changes to correct design defects in the breech to reduce the effect of firing stresses.
From the 1920s the carriage was upgraded first to Mk 1R (solid rubber tyres) then to Mk 1P (new wheels, axles, brakes and pneumatic tyres) for vehicle towing. Two versions of this appeared, in one stub axles were fitted below the original axle, later an entirely new axle was introduced. The similarly wheeled No. 26 artillery trailer was introduced to replace the limber. Unlike most other guns and howitzers in British service, calibrating Probert sights were not fitted to the 4.5-inch howitzer.
Production [ edit | edit source ]
By the outbreak of war in 1914, 192 guns had been produced, 39 being for imperial forces, this was less than ordered. Γ] Coventry Ordnance Works was the main supplier, with Ordnance Factory Woolwich producing substantial numbers. Other suppliers of complete equipments were Bethlehem Steel and before the outbreak of war a small number from Vickers. The Austin Motor Company produced some carriages. Total wartime production was 3384 guns (i.e. barrels) and 3437 carriages. 400 4.5-inch howitzers were supplied to Russia in 1916–17. Δ]
Cook Brothers had developed an unusual vehicle for desert conditions. This had two four-wheel-drive bogies each with its own engine. Steering was by pivoting the front bogie. They then developed their design into a tank destroyer with two engines at the rear. There was sufficient interest from the Army for a contract for development as the T55. Testing led to modifications to the pilot as the T55E1. Further testing confirmed that it was not suitable and the T55E1 was cancelled.
Power was from two Cadillac eight-cylinder water-cooled engines. Production began in 1943, however by this time preference had shifted to anti-tank vehicles, and the T55E1 was cancelled.
The M1 equipped 16 [ 2 ] or 17 [ 6 ] field artillery battalions in the Northwest Europe, where it was employed for corps support. M5 High Speed Tractor was assigned as prime mover. The weapon was declared obsolete in September 1945. [ 1 ] [ 2 ]
The gun had good range, nearly five km longer than its 155 mm howitzer sibling and longer then the 155 mm Gun M1918MI. It was out-ranged by another 155 mm gun, the Long Tom, but the latter was nearly three times heavier.
On the other side, the 4.5 inch gun was criticized for insufficient power of its high explosive shell. The shell was produced from low grade ("19 ton") steel, which necessitated thick walls. As a result, it carried only about two kg of TNT or substitute, in fact less than the 105 mm high explosive shell. Additionally, it was felt that having a small number of guns of atypical caliber unnecessarily complicated logistics. [ 1 ] [ 2 ]