105mm Howitzer Motor Carriage M7.

It's obvious how the 105mm HMC M7 acquired the nickname of "Priest" when one notes the pulpit-like .50cal machine gun mount to the right of the howitzer. This machine has the early three-piece final drive and differential cover and the early suspension bogies with smaller springs and return rollers directly on top of the bogie frames. The final drive and differential cover has the notch in the upper right corner to provide room for the medium tank M3's 75mm gun. Track grousers are stowed in the boxes on the hull front, and additional stowage boxes are mounted on the hull rear. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

Design changes were approved on 5 May 1942 that included adding a lower section to the machine gun position, thereby increasing room for the machine gunner. (Picture from TM 9-2800 Standard Military Motor Vehicles.)

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105mm Howitzer Motor Carriage M7.

The crew mounted the vehicle over the side, and grip bars were provided on both sides to ease this task. The machine gun is stowed in its travel lock. Note the riveted lower hull between the suspension bogies. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

This later-production machine showcases improvements inherited from the medium tank program such as the single-piece final drive and differential cover and heavy-duty suspension bogies. Hinged armor flaps have been added to the sides to protect the howitzer ammunition. Note also the changed location of the headlights and track grouser stowage boxes. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

The rearward position of the track return rollers and the folding armor plates are more easily seen in this side view. Baskets have been added to the stowage boxes on the hull rear. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

The ordnance was offset to the vehicle's right, which can easily be seen in this head-on view. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

The rear of the carriage is reminiscent of the medium tank M3 whence it was derived. Stowage boxes are mounted on the rear outboard corners of the hull. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7 at the at the Virginia Museum of Military Vehicles.

The rear of a restored vehicle is shown here and can be compared with the technical manual illustration.

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105mm Howitzer Motor Carriage M7.

Note the different rear armor plate configuration on this later-production machine. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

The positioning of the machine gun and howitzer relative to the crew compartment can be seen in this overhead view. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

Pioneer tools were stowed on the rear hull, and the positioning of the howitzer mount can be seen. The mount was installed facing slightly to the right in order to increase the available traverse when in the motor carriage. Note that there are enough folding seats for the entire crew. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

Ammunition stowage for an early-production vehicle is detailed in this diagram. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

Howitzer ammunition is shown here present in its racks. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

In this late carriage, additional ammunition racks have replaced four of the folding crew seats. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

Like all American self-propelled artillery of the era, the M7 was open-topped. A canvas cover could be mounted when needed. Separate covers were also available for the machine gun and howitzer breech. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

The cover for the mounted machine gun is shown here. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

Details of the radial engine are labeled as seen through the open rear engine compartment doors. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

The same view from a late-production machine can be compared. A. Main scavenger outlet tube. B. Oil line inlet tube. C. Fuel pump. D. Cranking motor wiring harness. E. Fuel inlet tube. F. Primer distributor line. G. Carburetor. H. Lower air intake tube. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

Two 12-volt storage batteries were connected in series to create a 24-volt electrical system. The battery compartment was under the left side of the crew compartment floor. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

Two vertical fuel tanks of 30gal (110L) capacity each and two horizontal tanks of 58gal (220L) capacity each were located in the engine compartment. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

The front air inlet shutter in the front engine cover plate allowed the amount of cooling air ingested into the engine compartment to be regulated. The vanes could be moved from fully open to fully closed. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

Similarly, an outlet shutter above the rear engine doors regulated how much cooling air was expelled. Note the exhaust deflector on this late-production carriage, which is raised and secured out of the way. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

The driver was seated below and to the left of the howitzer mount. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

Changes made during production to the driver's position can be gleaned from comparison with this picture. A. Driver's door. B. Protectoscope. C. Compass. D. Primer pump. E. Hand throttle. F. Horn switch. G. Steering brake control levers. H. Gearshift lever. J. Tachometer adapter. K. Accelerator pedal. L. Driver's seat. M. Clutch pedal. N. Instrument panel. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

The installation of the driver's protectoscope is illustrated in this picture. A. Driver's door. B. Rotor handle. C. Rotor window support. D. Cage attaching bolt. E. Hinge. F. Indirect vision rotor. G. Protectoscope. H. Door support. J. Door latch handle. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

Details of the machine gun mount can be seen in this image. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

The 105mm howitzer M2A1 is shown here in its mount M4. The weight of the howitzer tube and its breech mechanism was ~1064lb (~482.6kg). (Picture from TM 9-1325 105-mm Howitzers M2 and M2A1; Carriages M2A1 and M2A1; and Combat Vehicle Mounts M3 and M4.)

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105mm Howitzer Motor Carriage M7.

Details of the howitzer mount are given here. It took 35.5 revolutions of the elevation handwheel to elevate the howitzer 20°, and 19 revolutions of the traverse handwheel to traverse the ordnance 20°. Note that an elevation handwheel was provided on each side of the howitzer mount. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

The only way the howitzer would fire was by pulling the lanyard. As a safety feature, if the ordnance failed to completely return to battery, the lug on the firing shaft would not engage with the trigger shaft. (Picture from TM 9-731E Carriage, Motor, 105-mm Howitzer, M7.)

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105mm Howitzer Motor Carriage M7.

The howitzer cradle weighed 333lb (151kg). (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

The recoil mechanism and sleigh are shown here with the ordnance dismounted. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

A cross-section of the recoil system is diagrammed in this picture. The recoil mechanism weighed 463lb (210kg), with the recuperator weighing 72lb (33kg). The normal recoil stroke was 42" (110cm). (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

An exploded view of the beech mechanism is shown here. In contrast to that found on the 105mm howitzer M2, the breech ring of the howitzer M2A1 had two bronze bearing strips inserted into dovetail slots cut into the bottom of the breech ring that were secured by four flathead screws. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

The howitzer travel lock was disengaged by turning the traveling lock lever counterclockwise until socket "B" cleared the locking shaft ball end. The howitzer was then traversed until socket "A" was clear of the lock, and once this occurred the traveling lock bracket was lifted out and stowed. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7.

The sighting equipment is shown installed in this picture. (Picture from TM 9-731E 105-mm Howitzer Motor Carriage M7.)

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105mm Howitzer Motor Carriage M7 at the at the Virginia Museum of Military Vehicles.

Some of the instruments labeled above can be seen in this image of a museum vehicle.

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105mm Howitzer Motor Carriage M7.

Crew positions are show here mounted (left) and ready for action (right). (Picture from FM 17-63 Service of the Piece, 105-mm Howitzer, Self-Propelled.)

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105mm Howitzer Motor Carriage M7B1 at the Patton Museum of Cavalry and Armor.

This is an M7B1, sporting the one-piece final drive and differential housing, heavy-duty suspension bogies, and fold-up armor towards the rear of the hull. Stowage baskets are present on top of the rear stowage boxes.

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105mm Howitzer Motor Carriage M7B1 at the Patton Museum of Cavalry and Armor.

Late-model M7s were quite similar to the M7B1, but this rear view establishes that this vehicle is derived from the M4A3 Sherman, marking it as the latter. The rear plate dips below the sponson line, the rear hull extends over the fenders behind the stowage boxes, and the exhaust deflector grid can be seen below the rear plate. The rear stowage boxes and baskets are visible, as are handles on the side of the hull. Attachment points for various tools are welded to the rear plate.

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105mm Howitzer Motor Carriage M7B2 at the West Virginia National Guard Headquarters.

Compared with the M7B1 above, it is easy to see how this M7B2's howitzer has been raised, resulting in more elevation. The machine gun pulpit has had another section added to ensure a complete field of fire over the howitzer.

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105mm Howitzer Motor Carriage M7B2 at the West Virginia National Guard Headquarters.

This side view provides a better view of the raised MG position. The folding armor flaps can also be seen behind the MG pulpit, above the side hull handles.

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105mm Howitzer Motor Carriage M7B2 at the West Virginia National Guard Headquarters.

Like the medium tank M4A3 from which it was derived, the engine grill doors on this M7B2 run totally across the rear deck. The rear hinged armor plate is folded down, and is visible to the left in the picture.

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105mm Howitzer Motor Carriage M7B2 at the West Virginia National Guard Headquarters.

The driver's door is open on this vehicle, and this is a view through it into the interior. One circular seat for a member of the gun crew remains on the vehicle's left, and the mount for a portable fire extinguisher is visible in the left rear corner of the fighting compartment. One hundred-five millimeter ammunition racks line the hull sides, and the howitzer mount can be seen to the driver's right.

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105mm Howitzer Motor Carriage M7B2 at the West Virginia National Guard Headquarters.

The M7B2 used driving controls common to the M4A3 tank, and they are illustrated here. The steering levers are in front of the driver's seat, and the gearshift lever is to the driver's right. The transmission itself is visible beside the driver's position.

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105mm Howitzer Motor Carriage M7B2 at the West Virginia National Guard Headquarters.

The 105mm howitzer M2A1 was mounted in the M7B2 by sticking the top half of the standard field carriage in the fighting compartment. The breech handle can be seen sticking up above the front of the breech. The handwheel to the front was for azimuth, and the elevation handwheel is to the rear. The howitzer shield can be seen on either side of the ordnance's barrel. The open driver's door is visible to the howitzer's left, and the inside of the machine gun position is visible to the right.

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105mm Howitzer Motor Carriage M7B2 at the West Virginia National Guard Headquarters.

The heavy-duty suspension bogies carried over from the medium tanks M3 and M4 had both track return rollers and track skids. The skid design changed with modifications to the bogie, and this vehicle is equipped with the final design. Since the front of the track skid makes a loop and runs to the rear before it reaches the bogie frame, it indicates that the this bogie has its trunnion centers raised from earlier types, which improved spring stability. The front volute spring can also be seen.

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105mm Howitzer Motor Carriage M7B2 at the West Virginia National Guard Headquarters.

The innards of a vertical volute spring suspension bogie are illustrated here. The support bracket for the track return roller is visible at the top, and one of the volute springs can be seen in the center of the picture. Rubbing plates were positioned between the ends of the top lever and wheel arm, and the rubbing plate retaining screw can be seen at the end of the top lever.

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105mm Howitzer Motor Carriage M7B2.

Postwar, another cannoneer was added to the vehicle. He is number 5 in these images. (Picture from FM 6-74 105-mm Howitzer M2A1 on Motor Carriage M7B1 and M7B2.)

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Last updated 3 Oct 2021.
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