General Lucius Clay spoke out against this idea, due to it lacking mobility and having an estimated mass of 77 tons.

The chassis was inspired by the Heavy Tank T26, the turret and armament were similar to those of the M6A2E1.

The primary enemy of the future T29 would have been the Tiger II, which had a 150 mm thick upper glacis plate.

The 155 mm M1A1 gun, known as the Long Tom, was chosen as the starting point for this weapon.

Few operations in North Africa and Europe were performed without the Long Tom taking part.

Unlike its brother, which was scheduled to be produced in a series of 1200 tanks, the T30 was never going to be ordered in bulk.

This indicates that the T30 was always going to be a backup plan and was chiefly meant to test the 155 mm gun, which was given the index T7.

It was clear that the heavy tanks would be late to the war, and not only was the volume of the orders reduced, but the chassis was revised.

However, even initial estimates showed that the power to weight ratio of the T29 and T30 would be low, and a new engine was suggested: the air cooled 29 L Continental AV-1790.

The first prototype T30 tank was completed in March 1945 and received the registration number USA 30162842.

Even though some of the tanks spent only a few months or even weeks at the proving grounds, they were all broken in.

The engine and transmission had to be replaced during trials, but nevertheless the AV-1790 showed itself to be much more reliable than the Ford GAC.

Surprisingly, the T30 was the longest lasting among the experimental American heavy tanks.

[7] The 155 mm (6.1 in) gun fired separate loading (shell and charge) ammunition.

The high, rounded edge, turret was needed to accommodate the standing loader and large gun mount.

It could carry a mixed assortment of 34 T35E1 HVAP (high-velocity armor piercing), M112B1 and T29E1 APCBC-HE (armor-piercing capped ballistic cap high-explosive) M107 HE (high explosive), or M110 WP (Smoke) rounds.

[9] One pilot model, designated T30E1, had a semi-automatic system added to assist the loader in ramming the ammunition into the breech.

An additional hatch at the back of the turret was added for the automatic ejection of the empty shell casings.

Four are surviving examples; one each at the U.S. Army Armor and Cavalry Collection, Fort Moore, Georgia.

[12] the Detroit Arsenal in Warren, Michigan,[citation needed] at Fort Jackson, South Carolina[13] and in Aberdeen Proving Grounds