Not a shotgun, but the USSR developed an entire aircraft with EO-guided turret-mounted 23mm cannon to counter balloons. The Myasischev M-17: https://3.bp.blog

Not a shotgun, but the USSR developed an entire aircraft with EO-guided turret-mounted 23mm cannon to counter balloons. The Myasischev M-17: https://3.bp.blogspot.com/-ad9rmXHhi2U/TaBxNpJvBtI/AAAAAAABIx0/FwyRIf6lXj8/s1600/M17-07.jpg https://3.bp.blogspot.com/-ad9rmXHhi2U/TaBxNpJvBtI/AAAAAAABI... Over 4,000 recce balloons had entered their airspace up until the late 1970s and the Soviets compiled statistics that "on average 1.4 guided AAM's, 26 unguided rockets and 112 cannon rounds were used against each [destroyed] balloon"