U.S.S. Allen M. Sumner DD-692
Main Battery

5 inch/38 caliber Mark 12 Dual Purpose Gun

Installed during construction and retained throughout her active service, Sumner deployed 6 5"/38 Mk 12 guns housed in three Mk 38 twin mounts with two forward and one aft. The after mount could actually fire forward of the ship! Ammunition was supplied from the magazines via the "ready service ammunition handling ring," also known as the "merry-go-round" which was located immediately below the mount. The guns could be aimed and fired either from automatic control or in manual mode. The mounts could be trained at a rate of 25 degrees per second and elevated from -15 degrees to 85 degrees at a rate of 15 degrees a second. They were capable of fire at any angle with an experienced crew able to sustain a 15 round per minute fire rate. This rate could rise to 22 rounds per minute at optimum loading angles. Range of this weapon was 18,200 yards with a ceiling of 37,200 feet. All of the following views are of the these guns as they appeared aboard the Sumner.

Forward Mounts 51 & 52
Aft Mount 53
General views over the years

5"/38 Ammunition

The basic round for the 5"/38 Mk 12 gun was semifixed with a projectile and a powder cartridge. The projectiles normally used were the Common (COM), High Capacity (HC) and Antiaircraft Common (AAC). There were also special rounds such as Special Common, Illuminating (ILLUM), Window (W) and White Phosphorus (WP). Depending on type they weighed approximately 54 pounds. Various fuzes could be used with the projectiles such as the VT or proximity fuze with other examples being the Mechanical Time Fuze, Point Detonating Fuze and Base Detonating Fuse.  A Rocket Assisted Projectile was introduced in 1968 but it is uncertain if any ever made it aboard the Sumner.
Projectiles being loaded while underway off Vietnam

The powder cartridge contained approximately 15 pounds of powder in a 12 pound shell and was usually either SPDN (smokeless) or SPDF (smokeless/flashless) with use depending on the amount of light. Each cartridge was stored in an aluminum can that made it easy to move and store. The powder was made from an ether-alcohol colloid of purified nitrocellulose to which other ingredients could be added such as Ethyl Centralite, Diphenylamine or Potassium Sulfate. My ears will attest to the rather large "BANG" experienced when these charges were ignited!

Empty aluminum powder cans litter the decks after NGFS in Vietnam


A practice 5"/38 loading machine was located on the Torpedo Deck where new hands learned the basics of feeding a 5"/38.

Fire Control

The Fire Control system for the 5"/38 aboard Sumner changed over the years with the advances in electronics. Developed in the 1930's the Mk 37 GFCS was installed first with the Mk 4 radar and then the Mk 12/22 radar in 1945. The radar was again replaced in 1950's by the Mk 25. This unit fed a whole range of computers including the Mk 1 and Mk 1A Computers, Mk 6 Stable Element, Mk 1 Star-Shell Computer, the Fire-Control Switchboard and Illumination Control. Further understanding in this area can be had by purchasing a few Buds for your friendly Firecontrolman.
The Mk 12/22 radar The Mk 25 radar

The guns in action

All of these views are from combat off Vietnam

Many thanks to Charlie Blackburn, Glen Burdett, Al Payne, Arne Schumacher, Harold Jackson, Ralph Stamp, Gary Vogel, Eric Bollin, Richard Borutta, Dolphus Burton, Gary Carnot, Gary Jensen, Billy Johnson, Bob Misiano, Mike Raatjes, Doug Seal and Hank Lunki for sharing these images with us.