The military models were equipped with a 7.62 mm (.30 in) ShKAS machine gun, and later with a 12.7 mm (.50 in) UBK heavy machine gun.
IS-2 – The second airframe with improvements and M-88 engine in a long-chord NACA cowling, armed with 2x BS and 2x ShKAS.
A one-second burst from four ShKAS in Polikarpov I-153 or Polikarpov I-16 placed 120 bullets within 15 angular mils at 400 meters (1,312 feet) giving a firing density of 5 bullets per square meter of the sky.