The M1 Underwater Defense Gun, also called the Underwater Defense Gun Mark 1 Mod 0, is an
underwater firearm developed by the United States during the
Cold War
The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because t ...
. Similar to other underwater firearms, it fires a special metal dart as its projectile.
History
The gun was developed as part of a project called TDP 3801 during the 1960s, and much of the work on it occurred at the Naval Surface Weapons Center White Oak Laboratory in
Silver Spring, Maryland
Silver Spring is a census-designated place (CDP) in southeastern Montgomery County, Maryland, United States, near Washington, D.C. Although officially unincorporated, in practice it is an edge city, with a population of 81,015 at the 2020 ce ...
. Originally, the idea was for the LanceJet, a rocket-based weapon similar to the
Gyrojet
The Gyrojet is a family of unique firearms developed in the 1960s named for the method of gyroscopically stabilizing its projectiles. Rather than inert bullets, Gyrojets fire small rockets called Microjets which have little recoil and do not req ...
family of firearms, but rocket-powered weapons proved to be expensive and inaccurate, so alternatives were researched. The result was the Mk 1 Underwater Defense Gun, introduced in the early 1970s. It proved effective but, says Tom Hawkins of the nonprofit Naval Special Warfare Foundation, "It was bulky and heavy and the men never warmed up to it. It was also a signature controlled item -- as in signing your name to check it out -- and administratively a burden to the operational units."
In 1976, the
Heckler & Koch P11 was introduced, and it soon replaced the Mk 1.
Design
The Mk 1 is a
double action only pepper-box
The pepper-box revolver or simply pepperbox (also "pepper-pot", from its resemblance to the household pepper shakers) is a multiple-barrel firearm, mostly in the form of a handgun, that has three or more gun barrels in a coaxially revolving me ...
weapon, and its removable cylinder magazine fits into the side of a gun, being inserted and removed through a door on the left side of the gun. The frame, cylinder, door assembly, and action are made of aluminum, the trigger is made of self-lubricating nylon, and all other parts are made of stainless steel. The magazine holds six rounds.
Mark 59 Mod 0 Projectile
The distinctive cartridge fired by the M1 is the Mark 59, a stainless steel cylinder containing a single long heavy tungsten dart. Near the base of the cylinder is the firing assembly, and when the firing pin strikes the primer, the propellant, contained in a chamber below the firing assembly, ignites and propels the dart out of the cylinder.
The dart itself is long and thin, and it has four fins machined into its rear section, with each fin having a small angle cut into it that causes water to flow over it and give the projectile a stabilizing spin. The shape of the dart helps it to penetrate the water while retaining a high velocity.
The self-contained design of the Mark 59 contributes to the propellant gases being kept in the cartridge, which eliminates muzzle blast that could produce a dangerous shock wave. It also has the side effect of eliminating muzzle flash and reducing sound, so that the weapon can function as an emergency covert weapon if necessary, although this was rare because of the high cost of the ammunition.
See also
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Notes
References
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{{Underwater diving, prodiv
Multiple-barrel firearms
Underwater pistols
Cold War weapons of the United States
Flechette firearms
Military equipment introduced in the 1970s