The T30 was developed for the American Army during the latter stages of World War 2 to counter the appearance of German Army heavy tanks during Nazi Germany's "last gasp" in 1945. The T30, along with the similar T29, followed behind the T28 Super Heavy Tank development. While the T28 was essentially more akin to a self-propelled gun, the T30 and T29 designs utilized a turreted layout and were much lighter than their four-tracked forerunner - however still heavily armed and armored. Prototypes (known in the tank world as "pilots") of the T30 were being designed as early as April of 1945 - this turning out to be the end of the war in Europe - though completed forms were not made available until 1947. By then, the war in the Pacific had also concluded leaving the T28, T29 and T30 designs in limbo. Eventually, all heavy tank projects (as well as a myriad of other interesting wartime developments) were cancelled with surviving examples inevitably becoming museum pieces in the Fort Knox, Kentucky area.
The T30 made use of one of the largest guns ever fitted to an American tank - this being a 155mm T7 L/40 main gun. The main gun was fitted into a fully traversing turret protected by slab sided surfaces with rounded edges, giving the entire tank a rather high, however necessary, profile. The barrel was capped at the muzzle with a baffled muzzle brake to content with the main gun's recoil. Thirty-four projectiles of 155mm ammunition were afforded the system and crew and would have comprised both armor-piercing (AP) and high-explosive (HE) types. The main gun was supplemented by 0.50 caliber, coaxially-mounted Browning HB M-2 machine gun as well as a Browning M1919A4 0.30 caliber, bow-mounted general purpose machine gun.
The turret was set onto a conventionally arranged chassis featuring a tracked wheel assembly dominated by eight road wheels to a track side. Suspension was torsion-bar oriented and each track width was noticeably wide to contend with varying soil types. A well-sloped glacis plate protected the front of the tank by helping to deflect any incoming enemy shells by supplying awkward angles. The chassis was powered by a single Continental-brand AV1790-3 series, air-cooled, gasoline engine of 704 horsepower output. This provided for speeds up to 16.5 miles per hour on paved road surfaces, though lesser so when heading off-road.
The T30 weighed in at roughly 145,000lbs (72.5 tons). Her length was listed at 37 feet, 11.5 inches with a width of 12 feet, 5.5 inches and a height equal to 10 feet, 6 inches. A crew of six would have managed her various critical stations on the battlefield had she ever gone into production and operational service. These crew positions would have encompassed the tank commander, driver, two loaders, a gunner and a bow machine gunner. The two loaders were needed to operate and maintain the special loading function concerning the large 155mm projectiles - each weighing in at 98lbs. One loader managed the integrated crane responsible for maneuvering each shell into position while the other operated the rammer responsible for moving the shell into the firing chamber. Armor protection across all facings of the tank ran from 25mm (0.98 inches) to 280mm (11 inches) in thickness.
The T30 was also developed into a revised variant under the designation of T30E1. This model added another hatch at the rear of the turret to help facilitate the ejecting of the large spent 155mm shell casings after firing. There was also another lesser-detailed development falling under the prototype designation of T30E2. Still another variant, the T57, was developed with an oscillating turret housing an automatic loader for the main gun - an interesting development in that automatic loaders eventually proved more popular with modern Soviet tank systems; the Americans choosing instead to keep the reliable and less-complicated manual loading process as a part of their future tank designs for decades to come.
The validity of "super heavy tank" designs was never wholly proven in World War 2. The Germans continued development of several such designs up to the end of the war but no prototypes ever reached the production stage. Similarly, the British only reached trials with their "Tortoise" Assault Tank while the T28, T29 and T30 designs for the Americans were all abandoned in time after the war. Many of these mammoth designs ultimately proved either too unreliable, too unwieldy or simply too heavy to traverse the landscapes of Europe with any normalcy, not to mention the rather tight confines of the roads and bridges to be encountered across France and Germany. Transportation by railways was always an option - albeit a complicated, time consuming one. Even top speeds along roads would have proved equally limiting, with many of these heavy tank designs failing to match that of their more mobile medium tank counterparts, in a way making them oversized liabilities in the new era of flexible mechanized warfare.
If anything, such heavy tank designs served to push the envelope for future tank developments, serving as testbeds for new armor configurations and optimized track-and-wheel arrangements as well as proving useful for the testing of various armament layouts. For example, the T30 ultimately served to evaluate the Continental AV1790 engine which ended up being used in upgraded M26 Pershings during the Korean War (1950-1953) and ultimately proved the powerplant effective for the upcoming M46 Patton, M47 (Patton II) and M48 Patton main battle tank series. In a converted diesel form, the engine went on to serve in the Cold War-era M60 (Patton) main battle tank.
As of this writing, the T30 Heavy Tank can be seen at outside of Marshall Hall at Fort Knox, Kentucky.