It was, by 1941, lacking in all major areas, except rate of fire. Nevertheless, since neither the 20mm Oerlikon nor the 28mm nor 40mm guns could be procured in large enough numbers, it remained an important stay of the air defense departments of many ships, including the carrier Lexington at the Coral Sea battle. It had, however, become a revenge weapon at best, as it was unlikely that an incoming torpedo planes or dive bomber would come close enough before the release of his weapon to be damaged or even shot down.

    Aboard ships, the weapon generally in use was water-cooled and this weapon is described here. Many of the weapons removed from updated ships and many new build guns were employed aboard submarines, landing craft and landing support craft, patrol boats and subchasers.

   The gun employed no high explosive bullets, but a variety of others, including solid, tracer, and incendiary.