Weapon History - Mk 22 Mod 0 "Hush Puppy" - The Silent Legend of the SEALs

In the depths of the Vietnamese jungle and in the shadow of secret operations, a weapon evolved into a silent symbol of the special forces: the Mk 22 Mod 0, better known by its codename "Hush Puppy." This specially adapted variant of the Smith & Wesson Model 39 was designed in the 1960s for the needs of the US Navy SEALs – with a clear goal: maximum noise suppression when taking out enemy sentries and dogs.

Origin and Development

The original M39 was a semi-automatic pistol in 9 mm caliber with a single-stack magazine, which first appeared on the civilian market in the mid-1950s. For the newly established SEAL teams, this model proved to be an ideal platform due to its compact design and reliability. At the request of the units, a modified version with a silencer was developed by the Naval Ordnance Laboratory – the birth of the Mk 22 Mod 0.

The joking nickname "Hush Puppy" – meaning "quiet puppy" – reflected its primary purpose: the discreet elimination of guard dogs before SEALs infiltrated enemy territory unnoticed.

Technical Features

What distinguished the Mk 22 from its original version was a whole package of targeted modifications:

• Extended barrel with threads, to which the specially designed Mark 3 suppressor was mounted.
• Slide lock to prevent the automatic cycling process – a key element to eliminate even the last mechanical noise.
• Higher sights, which allowed for precise aiming despite the bulky suppressor.
• Redesigned magazine well for a double-stack magazine, initially that of the Browning Hi-Power, later a proprietary 14-round magazine from Smith & Wesson.
• Removal of the magazine safety on many service pistols – often removed unilaterally by the SEALs.
• Robust plastic grip panels instead of the classic wooden variants.
• Prototype wire stock, which, however, was never widely introduced.

Silencer and Subsonic Ammunition

The centerpiece of the system was the Mark 3 Mod 0 silencer with innovative wipe technology: Several flexible plastic discs effectively sealed the gas flow and ensured an extremely quiet muzzle sound. However, the wipes had to be replaced regularly – usually after 24 to 50 shots.

In conjunction, a special subsonic ammunition (Mk 144 Mod 0) with a heavy 158-grain bullet was used. This remained just below the speed of sound but was powerful enough to function reliably. Additionally, it was waterproof sealed – ideal for amphibious operations.

Operational Tactics and Accessories

The "Hush Puppy" system was designed as a complete kit: pistol, silencer, spare magazine, and maintenance accessories were delivered waterproof in the M19A1 ammunition container. A separate operational kit with spare parts and subsonic ammunition (Mk 26 Mod 0) rounded out the setup.

In the field, the procedure was clearly defined: with the slide locked and the silencer attached, a targeted, nearly silent shot was fired – perfect for covert operations in enemy territory. Each subsequent shot had to be manually reloaded – a conscious compromise in favor of maximum noise minimization.

Historical Significance

Starting in 1967, the Mk 22 found its way into the hands of SEAL operators in Vietnam – initially in small numbers, later increasingly widespread. Its efficiency in jungle warfare quickly made it an indispensable tool for covert operations. Despite later wear and technical obsolescence, the "Hush Puppy" remained in the memory of the SEALs as a symbol of tactical precision and engineering sophistication.

Conclusion

The Mk 22 Mod 0 was more than a suppressed pistol – it was a custom tool in the arsenal of shadow warriors. Its design influenced future developments in the field of specialized service pistols. To this day, the “Hush Puppy” stands as an example of how a civilian model can become a silent legend.

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