The test tank KV-2 gun with the ZIS-6 tank gun of increased power, created by Soviet designers, under the leadership of Basil Gavrilovic hrabina designed for tanks KV-3, KV-4 and KV-5, which never went to series. In early may 1941 the prototype gun ZIS-6 was installed in the tower tank KV-2. May 14, 1941, was made the first shot.
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