The Silent Sniper System was an American experimental sniper rifle.
In August of 1967, the U.S. Army Limited War Laboratory (USALWL, or LWL) began initial development on a silenced sniping weapon as part of continued efforts to help improve sniper capabilities. The AAI Corporation was contracted to manufacture the weapon, of which they produced six prototypes.
Two of the rifles, with two-thousand rounds of subsonic ammunition, were delivered to Vietnam for testing and evaluation purposes in 1971. After delivery, LWL reported that any further development would be handled by the U.S. Army Weapons Command.
The weapon proved to be unpopular with the troops, because of its large size and bulk. Snipers were not confident of being able to land killing shots out to 250 meters and beyond using the rifle. Most wished to drop out of testing it and to instead use XM21 sniper rifles equipped with Sionics sound suppressors.
The Silent Sniper System was based on a Winchester Model 70 bolt-action rifle chambered in .458 caliber to use a specialized subsonic cartridge, with the barrel modified for noise reduction.
For its standard sighting system, it uses LWL's Adjustable Ranging Telescope (ART) with the ballistic cam tailored to the ballistics of the cartridge's 500-grain (32.39 grams) projectile. There is also a provision for an alternate sighting system; An adapter mount base for using a Starlight night vision scope.
With its silenced barrel, the weapon's firing signature would be inaudible beyond 100 meters.