 Another T1 test gun was produced with the barrel shortened and a counterweight added to the breech to improve balance.The reduction in length by did not reduce performance; penetration was the same as the 3 inch gun.By August 17, the Ordnance Department had classified the test gun with the shorter barrel as the 76-mm M1  and set up the precedent for the designation of M4 tanks armed with the gun to include "(76M1)".