The Mark 12 5"/38 caliber gun was a United States dual-purpose naval gun, but also installed in single-purpose mounts on a handful of ships. The 38 caliber barrel was a mid-length compromise between the previous United States standard 5"/51 low-angle gun and 5"/25 anti-aircraft gun. United States naval gun terminology indicates the gun fired a projectile 5 inches (127 mm) in diameter, and the barrel was 38 calibers long. The increased barrel length provided greatly improved performance in both anti-aircraft and anti-surface roles compared to the 5"/25 gun. However, except for the barrel length and the use of semi-fixed ammunition, the 5"/38 gun was derived from the 5"/25 gun. Both weapons had power ramming, which enabled rapid fire at high angles against aircraft. The 5"/38 entered service on USS Farragut, commissioned in 1934, the first new destroyer design since the last Clemson was built in 1922. The base ring mount, which improved the effective rate of fire, entered service on USS Porter, commissioned in 1936.
Two Mk 30 single enclosed base ring mounts on USS David W. Taylor
Mk 12 gun assembly
Vertical Sliding Wedge Breech Block.
Drawing of the recoil and counter-recoil systems. The arrow shows the motion of the housing in the slide during recoil.
A dual-purpose gun is a naval artillery mounting designed to engage both surface and air targets.
The Mark 37 Modification 6 5-inch dual-purpose gun on display at the National Museum of the Pacific War. The gun had a range of over 6 miles and could fire 22 rounds a minute.
