AGS-M551

By the early 1980s, the Army concluded a more powerful weapon than the 75 mm gun required by the HIMAG program was necessary for the Army's light forces. Characteristics were outlined and revised, becoming known as the armored gun system (AGS). The search for a new weapon considered a 105 mm gun to be the most ideal candidate.

The Naval Surface Weapons Center experimented with installing the 105 mm Gun M68 in the turret of an M551 Sheridan and using the recoil system for the 152 mm gun-launcher. The cannon was trialed with and without a muzzle brake. Although this installation worked, it would have required significant development before it was satisfactory. The turret ring in particular couldn't quite handle the recoil force of the massive weapon and was damaged after some tests. However, it was deemed practical to mount a 105 mm on such a lightweight chassis. The development of such a new AGS was designated as the XM4, and several potential candidates were put forth.

The Cadillac Gage Company had been developing the Stingray light tank for the export market, but quickly realized it met the requirements for the XM4 program. It had a welded turret with a conventional crew arrangement. The gun used was a low-recoil force (LRF) variant of the Royal Ordnance 105 mm L7. The turret and gun were successfully tested on the chassis of an M551 Sheridan.

As I'm proposing it, the AGS-M551 is a combination of both of these projects. While this is technically a light tank, I think the stresses provided by the gun on the chassis makes it more in line with this particular branch of tank destroyers. The vehicle is extremely mobile, but I would expect the aim time, reload speed, turret traverse, and on-the-move dispersion would be relatively poor. This makes it more ideal for the tank destroyer role in my opinion, especially as the requirements of the AGS is comparable to the theme of this mobile, lightweight branch of tank destroyers.



Guns: 90 mm Gun M41; 105 mm Gun M68; Royal Ordnance 105 mm L7A3 LRF

Engines: GM 6V53T Early (275 hp); GM 6V53T Late (300 hp)

Turrets (Turret Armor (mm)): M551 Modified (38/15/15); Stingray (25/??/??)

Suspensions/Alternate Hulls, Total Weight (metric tons): M551 Sheridan (15.18); M551 Modified (??)

Hull Armor (mm): 15/32/13

Top Speed: 69 km/h

Crew: 4 (Driver; Gunner; Loader; Commander/Radio)

Parent: M41A1 Exp.
Children: Stingray
See Also: AGS-M41

Sources:

Hunnicutt, R. P. Sheridan, 2015.