They were one of a range of suppressed weapons deployed and found use assassinating enemy officers and Communist Chinese observers, during snatch raids to capture high-ranking prisoners and in shallow penetration raids into Laos and Cambodia. The pistols were put to use during a variety of operations including long-range reconnaissance patrols, snatch missions, ambushes, and assassinations. 22LR suppressed High Standard pistols were again used by both CIA operatives (including Air America pilots) and Special Forces members of the classified Studies and Observations Group, including the Navy SEALs and Army's Green Berets.

The mesh and wire screens would last for up to 200 rounds before they needed to be replaced.Дuring the Vietnam War, the. The suppressor could reduce the pistols report to as little as 20 decibels - about as quiet as a person whispering. This maximized the efficiency of the suppressor and the only sound heard when the pistol was fired was the mechanical function of the action. Closer to the muzzle, a second chamber was filled with bronze wire screens further slowing the exit of the gases.ДЄ common OSS trick was to fill the second chamber with liquids such as water, oil, or even shaving cream and seal the muzzle with tape. From these holes the propellant gases from the fired cartridge escaped into a zinc-plated bronze mesh, which acted as a heat sink that slowed the gases exit from the muzzle. The barrel was ported with four rows of eight (later 11) holes.

Unlike stock High Standard pistols the HDM/S had a slide lock that could be used to prevent the gun from making a sound by locking its action closed, making it a near silent single-shot weapon. These Impact Testing Machines were 13.8 inches in length, weighed 48 ounces unloaded, and had a 10-round magazine.

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