The The 90-mm M3 gun of the Pershing was similar to the German 88 mm KwK 36 used on the Tiger I. In an effort to match the firepower of the Königstiger's more powerful 88 mm KwK43, the T15E1 90 mm gun was developed and mounted in a T26E1 in January 1945. This tank was designated T26E1-1. The T15E1 gun was 73 calibers in length and had a much longer high capacity chamber. This gave it a muzzle velocity of 3,750 ft/s (1,140 m/s) with the T30E16 APCR shot and could penetrate the Panther's frontal armor at up to 2,600 yd (2,400 m). This model used a single piece 50 in (1,300 mm) long ammunition and was the only Super Pershing sent to Europe.
A second pilot tank was converted from a T26E3 and used a modified T15E2 gun that used a two piece ammunition. A total of 25 of these tanks were built and designated as the T26E4 Super Pershing. The front armor of the hull and turret are be rise up (turret on picture had no extra armor) to 178mm with armor plates. An improved mounting removed the need for stabilizer springs Post-war, two M26 tanks had the T54 gun installed, which had the same long gun barrel, but the ammunition cartridge was designed to be shorter and fatter, while still retaining the propellant force of the original round. They also had the muzzle brake and bore evacuator from the M3A1 gun of the M26A1 and M46. The tanks were designated as the M26E1 tank, but lack of funds cut off further production.
The T26E4 "Super Pershing" saw his debut in FHSW in version v0.2 together with the redesigned M26 Pershing. It was until v0.5 the heaviest American tank in the mod when this title goes to the T29