The Mk 1 Mod 0 Underwater Defense Gun, also known as the M1, was an American underwater revolver designed by John L. Crichter in 1967 and produced by AAI Corporation from 1970 to 1976. A highly-secretive weapon, the Mk 1 was the first American underwater firearm used in any capacity.

History[edit | edit source]

The Mk 1 was designed by John Crichter from AAI Corporation in 1967; however, most work occurred at the Naval Surface Weapons Center White Oak Laboratory based in Silver Spring, as part of project TDP 3801. The initial idea of the project was the LanceJet, an underwater derivative of the unsuccessful Gyrojet family of arms, but proved to be overly expensive to produce and inaccurate; as such, an alternative was proposed, and this became the Mk 1.[1]

The Mk 1 was met with the approval of the Naval Surface Weapons Center and entered service in 1970.[2] To maintain its secrecy, the weapon was signature-controlled (to use the weapon, one had to sign a slip of paper or something similar).[3] The weapon, while serviceable, had a mixed reception; one Tom Hawkins of the Naval Special Warfare Foundation said of the weapon: "The weapon worked quite well, but 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."[2]

The weapon was quickly replaced with the highly classified Heckler & Koch P11 beginning in 1976,[1] and by the 1980s was completely retired from service.[4]

Design Details[edit | edit source]

The Mk 1 Mod 0 is a pepperbox-styled underwater firearm. The weapon uses a rotating cylinder which loads into the weapon through an opening trapdoor on the left of the gun. The weapon's action, door, frame and cylinder are made of aluminum, while the trigger is made of a self-lubricating nylon; everything else on the weapon is made of stainless steel.[1]

When the trigger is pulled, pressure is released from a primer which fires a piston which fired the weapon; the cylinder would then rotate 60° to the next cartridge. The cylinder held six Mk 59 Mod 0 darts. The weapon had no muzzle flash and as such, was a very quiet gun.[1]

Ammunition[edit | edit source]

The weapons used the Mk 59 Mod 0 dart.

See also[edit | edit source]

References[edit | edit source]

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