The "Hush Puppy" - A Silent Icon of the SEAL Teams

Origin and Development of a Special Weapon

The “Hush Puppy,” officially designated as Mk 22 Mod 0, is a silent legend of military weaponry. It originated in the 1960s as a covert sidearm for the newly formed US Navy SEALs. Its foundation was the Smith & Wesson Model 39 – a semi-automatic 9mm pistol with a single-stack magazine. Although this model was originally developed for the US Army but was not initially adopted, it later found its way into the SEALs' arsenal – albeit in a heavily modified form.

The SEALs needed a quiet pistol to silently eliminate opponents during covert operations – particularly guard dogs, before they could raise the alarm. From this need arose the “Hush Puppy” – a fitting nickname that humorously referred to its primary function: the silent “calming” of guard dogs.

Technical Features and Modifications

The conversion of the M39 to the Mk 22 Mod 0 was far more than cosmetic. One of the most noticeable changes was the extended barrel with a threaded attachment for the suppressor. However, the true technical finesse was revealed in the slide lock lever – a manual system that blocked the slide's recoil. This allowed the pistol to fire in single-shot mode without any noise from cycling or casing ejection. This measure ensured that only the suppressed muzzle sound was audible – optimal for silent neutralization.

Further modifications:

• Raised sights for use despite the bulky suppressor.
• Grip adjustment for a 14-round magazine (originally based on the P35 of the Browning Hi-Power).
• Removal of the magazine safety by many SEALs – against regulations, but in favor of operational safety.
• Plastic grip panels instead of wood – more robust for harsh operational conditions.
• Rare prototypes with a folding stock for stabilization.

Thus, the Mk 22 was not just a conversion, but a targeted redevelopment based on existing technology.

Mark 3 Silencer and Subsonic Ammunition: The Silent Trio

The centerpiece of the “Hush Puppy” was the specially designed Mark 3 Mod 0 silencer. With its approximately 12.7 cm long aluminum housing and wipe capsules (made of plastic discs), it was possible to drastically reduce the muzzle noise. These wipes tightly encased the projectile, allowing for efficient gas cooling and dampening – however, they wore out after about 24–50 shots and had to be replaced.

Complementary to this, the Mk 144 Mod 0 subsonic ammunition was specifically developed. With a heavy 158-grain FMJ bullet and a muzzle velocity just below the speed of sound (≈290 m/s), the supersonic crack was avoided. The cartridge was also waterproof sealed – a must for amphibious SEAL operations.

Field Suitability and Tactical Use in the Vietnam War

The "Hush Puppy" was used in Vietnam starting in 1967 – initially in small numbers and during ongoing testing. In operation, it was a precision tool: The operator fired a quiet single shot with a locked bolt at short range – mostly against guard dogs or isolated sentries. The absence of automatic repetition was not a disadvantage, but part of the concealment concept.

The weapon's delivery package included a waterproof transport container (M19A1 box), a second magazine, maintenance accessories, and in separate kits also replacement wipe capsules and other sealing elements. The system was designed to be transported underwater and then immediately made operational.

The Hush Puppy was by no means a universal weapon: It was clearly designed for covert, targeted operations – a specialized tool for special forces.

Technical and Tactical Legacy

Although the Mk 22 disappeared from service in the 1980s – not least due to material fatigue and a lack of spare parts – its influence is still felt today. Modern special weapons like the Heckler & Koch Mk 23 Mod 0 adopted the concept of:

• subsonic ammunition,
• highly effective suppressors,
• optional slide lock mechanism
  – and made it operationally suitable for modern conflict scenarios.

In terms of weapon technology, the Mk 22 was also a pioneer: The development of a 14-round magazine based on the M39 later led to the S&W Model 59 – one of the first mass-produced high-capacity 9mm pistols.

Conclusion: A Myth in the Shadow of War

The “Hush Puppy” Mk 22 Mod 0 was more than just a weapon – it was a product of precise needs analysis, technical creativity, and tactical finesse. Its quiet presence made it an indispensable tool for covert operations, and its reputation still precedes it today. For many SEAL veterans, it remains a symbol of an era when improvisation and effectiveness on the battlefield made the difference – in complete silence.

Source:

This report is based on a contribution from Waka Custom Guns:
👉 The Hush Puppy Pistol – Silent Special Weapon of the Navy SEALs in the Vietnam War