M57 Point Defense Gun

The M57 Point Defense Gun is a 57mm fast-firing, dual-purpose point-defense gun developed by the UEF Navy originally for use on its naval ships for self-defense. Capable of engaging both fighters, bombers and even other ships (at close range). It was also used by the UEF Army as a static and towed anti-aircraft gun on airbases and the like. It proved very capable in both ship and ground roles, swatting fighters and bombers effectively. However it was later replaced by the M100 as the Navy sought for a gun more capable in engaging ships and increased engagement range. When the M100 began replacing the M57 on ships, many M57s were transferred to the Army instead for ground use.
It is commonly and usually seen in its twin barrel configuration with the Navy exclusively using twin mountings.