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XM104 SPH: If You Give A Scorpion Steroids
History:The XM104 came out of a need for a lightweight SPG to complement the new form of airmobile warfare being adopted in the late 1950s. Having the ability to bring a 105mm howitzer around on a plane, drop it with a parachute, and then drive it straight into battle was seen as a must, and so work began in 1955. The weapon chosen was the M102 105mm howitzer, then still in development as the XM102. A modified variant was developed, called the XM103, which was designed for vehicular use. This would become the M103 howitzer, used on the M82 Self-Propelled Howitzer. By 1960, the first prototypes were in production, though these were simply mock-ups to test the final configuration. Once these initial tests were complete, work began on a set of functional prototypes.
One of the mock-up test rigs.
Because the vehicle was to be both air-droppable and amphibious, the design was incredibly sparse, with literally no protection whatsoever for the crew. A large spade was attached to the rear for added protection against recoil when firing the gun in a stationary position. The engine was selected from the Ford M151 utility vehicle, and the transmission was similar to the M151’s as well. This gave it a good top speed and comfortable mobility, which was exactly what was needed.
In full stationary firing position, the vehicle would dig the spade into the ground, fold down the sides with the seats and guard rails, and elevate the gun, thereby giving it its full range of motion. When the sides were elevated for the crew to sit in, the gun had significantly less horizontal traverse. Ten rounds were carried on the vehicle, with more requiring separate ammunition carriers. The gun was significantly lighter and simpler than previous 105mm howitzers, but could fire all NATO standard 105mm ammunition.
Tests began in 1962 with a set of six prototypes, each slightly different than the other in order to test different configurations to see which was ideal. These trials continued until 1965 with mixed results. On one hand, the vehicle was light, compact, mobile, and carried exactly the kind of powerful 105mm gun the Army was looking for. It could successfully be airdropped and was fully amphibious, just as the requirements indicated. The gun was fast (for a howitzer), and was accurate well within the constraints of the vehicle’s properties. Unfortunately, the lack of protection for the crew, a high center of gravity, and high cost put this project firmly in the scrap heap, though one prototype was saved and now resides at the Fort Sill Artillery Museum in Oklahoma.
Description:The XM104 is very similar to the M56 Scorpion, just scaled up to fit the 105mm howitzer. The chassis is small, measuring only 4.1m long, 1.75m wide, and 1.75m tall (gun fully stowed). It is also lightweight at only 3.6 tons. It only carries 10 rounds, but this is more than some other tank destroyers carry (SU-5-1 and Semovente da 90/53), so it shouldn't be too much of an issue. It can use any NATO standard 105mm ammunition, which would mean it can fire the M67 HEAT shell, though with a longer barrel than, say, the M4 howitzer on the M4A3(105), it should have better velocity. It also has the ability to fire M327 HESH and M662 HEAT-FS, the latter being equal to DM12. These shells would put it far ahead of the M4A3(105)'s firepower, possibly moving the BR even higher. There is no secondary weapon, and there is no crew protection. The crew consists of four, each seated back-to-back in pairs on each side of the gun. While this vehicle was usually meant to be used in a static position with the spade in place, there are other SPGs which share a similar real-life role which are already in the game (SU-5-1, Semovente da 90/53, FV4005, etc.), so I think this would fit just fine. It would use its mobility as its armor, with a top speed of about 35 mph (56 km/h).
Main Armament: 105mm Howitzer XM103
Armor: None, though the side panels could count as “structural steel” armor
Ammo Count: 10 Shells
Engine: Ford M151 inline-4 gasoline, 66HP
Transmission: Allison GS-100-3, 4 forward/1 reverse
Top Speed: 56 km/h (35 mph)
Gun Movement: +75/-5 elevation/depression, 45 degrees traverse (above seats/seats down), Unknown/fixed with seats up
Crew: 4 (Driver, Commander, Gunner, Loader)
If there is anything I have missed or gotten incorrect, please let me know! I hope you enjoyed reading this, and I hope you will also check out my other suggestions! Thanks, and have a great day.
Army Research and Development, June 1962, v. 3, no. 6, p. 15. via https://babel.hathitrust.org/cgi/pt?id=mdp.39015078433268&view=1up&seq=169