Improved variant)(also called U-14) had two 76 mm F-34 cannons, and 85 mm of frontal armor. Vehicles were not taken in service primarily because they could not fight tanks (the KV-7s had only 15 degree gun traverse to each side) and could not combat concrete bunkers due to the small caliber of the guns. After the failure of the KV-7 it was decided to put one 152 mm gun in the casemate instead of three smaller guns; this led to the development of the SU-152.