When the US Army came to the realization that the new German tanks, Panthers and Tigers, were not only getting progressively tougher and deadlier, but were also becoming more numerous on the battlefield, they began to search for solutions to adequately deal with the threat. The 76 mm M1 gun was available and implemented onto their standard M4 Sherman tank, but the 76 mm firepower proved to be disappointing against the German tank armour. The search for a bigger gun was needed for the US tanks, and one solution was to simply add the turret of the developing M26 Pershing (then still known as T26) onto the M4 Sherman hull. The single prototype test in 1944 proved that the conversion could be done, however the overall project was cancelled once it was determined that the research and development time to test out the viability of the design in combat would not make the design come any faster than the newer M26 tank. oh wait. i copy this from Warthunder.com thank you so much but dont worry it SUCK! =)