M18 Tank Destroyer, Hellcat

Aberdeen Tank Museum

In December 1941 the Ordnance Department wanted a fast tank destroyer with a 37 mm gun, a Christie suspension, and a Wright Continental R-975 engine to be developed. The first 2 pilot models were completed in mid-1942 and were designated the T49 GMC. A M1 57 mm gun was installed in place of the 37 mm based on the experience of the British in North Africa. The Christie suspension was replaced by a torsion bar suspension. It was tested in July 1942, and the Tank Destroyer Command asked the Ordnance Department to have a 75 mm M3 gun installed.

The T49 was canceled and the new model became the T67 GMC. It had an open, rounded turret like the T67 GMC (M-10 prototypes). It was light at 20 tons, and with it's powerful engine it turned out to have very good performance. Based on this the Armored Vehicle Board recommended it for standardization.

The Tank Destroyer Command decided in February 1943, that it wanted to have the more powerful 76 mm M1 gun installed. Six prototypes were built similar to the T67 with the 76 mm gun and were designated the T70 GMC. As a result of the trials a new shape for the hull front and a new turret were designed. Production started in July 1943 at the Buick factory.

In February 1944, it was standardized as the M18 GMC.¹

Fastest AFV of World War II. Low silhouette, well slopped. It had a center guide track, torsion bar suspension, and an automatic transmission. Two escape hatches in the hull roof and in the floor.

Used by tank destroyer battalions in Europe.¹ It was intended to be used in an ambush roll with its quick speed.

It first saw action in the Summer of 1944 in Europe.¹ One unit to use it quite effectively was the 630th Tank Destroyer Battalion in July 1944 reported destroying 53 Panthers & Tigers and 15 self propelled guns with only a loss of 17 of their M18s.¹

Could penetrate 101 mm. Muzzle velocity 2,600 ft/sec.⁵ The AP shell weighed 15.4 lbs.⁵ It could fire a HE shell 14,000 yards.⁵

105 mm Howitzer Motor Carriage T88:

In August 1944, the Ordnance Department wanted to develop a vehicle with the 105 mm T12 howitzer. By December 1944, a pilot model was finished. It was identical to the M18 except for the gun and the sights. It was canceled in August 1945.

Armored Utility Vehicle T41 (M39):

In June 1944, it was suggested to use a modified M18 as a prime mover for the 3" M6 anti-tank gun, or a troop carrier. Two M18s had their turrets removed and internal layout modified. The prime mover was designated the T41 and the troop carrier T41E1. Had a ring for a .50 cal Browning MG installed in the front. Weighed 35,000 lb. Crew 2 plus 7 passengers. Height 5' 11". It was standardized as the M39 in early 1945.

76mm Gun Motor Carriage T86, T86E1, and T87 (Amphibious):

In January 1944, 2 pilot models of an amphibious version of the M-18 was developed based on experience in the Pacific. They had a large lightweight flotation hull installed. The T86 propelled itself in the water by it's tracks. The T86E1 was propelled by 2 26" propellers driven by power taken from the engine. The T86 turned out to have the better propulsion method and with some other changes, became the T87 which appeared in December 1944. It was still undergoing trials when the war ended.

Sources:

1. The Encyclopedia of Tanks and Armored Fighting Vehicles - The Comprehensive Guide to Over 900 Armored Fighting Vehicles From 1915 to the Present Day, General Editor: Christopher F. Foss, 2002
2. British and American Tanks of World War Two, The Complete Illustrated History of British, American, and Commonwealth Tanks 1933-1945, Peter Chamberlain and Chris Ellis, 1969
3. The Encyclopedia of Weapons of World War II, Chris Bishop, 1998
4. Jane's World War II Tanks and Fighting Vehicles The Complete Guide, Leland Ness, 2002
5. Tank Data, Aberdeen Proving Grounds Series, 1968?