Over the years I’ve written about many unique revolvers, but this one is up there with the oddest of them.
Sometime in the early 1970s, the U.S. Navy acquired a pistol to equip their divers (including the SEAL teams). This wasn’t a pistol to be used once they exited the water, however; it was designed to be used underwater, against other divers who might want to pick a fight. (Like, say, when we were tapping Soviet undersea cables?)
The Underwater Defense Gun Mark 1 Mod 0, as it was called, was technically a pepperbox (a cylinder comprised of both chambers and barrels) as opposed to a true revolver, but that’s a distinction which is lost on most folks. It fired the Mark 59 Mod 0 projectile, which was a 4-1/4″ long tungsten dart.
The propulsion of the dart was done by a primer and propellant, contained in a cylinder. While little is known about the exact construction of the cartridges, It’s assumed that they used a captive piston arrangement: the propellant pushes the piston in the cartridge, which in turn shoves the projectile out the barrel. The base of the captive piston seals off the cartridge mouth, keeping the expanded gases from exiting the barrel. It is conceptually the same as the Soviet “silent” round for the PSS pistol.
So rare is the gun that very few pictures of it exist. This article over at medium.com has several and a fairly good (for laypeople) explanation of the gun and its use.
-=[ Grant ]=-