 Being a dedicated anti-tank gun, the 76 mm had a much weaker high explosive shell than the existing 75 mm, and was not initially accepted by various U.S. armored division commanders, even though many had already been produced and were available.All of the U.S. Army M4s deployed initially in Normandy in June 1944 had the 75 mm gun.Tests against American armor plate suggested that the new M1A1 gun would be adequate, but testing against captured Panther tanks was never done.