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, with Barnes Bullets to produce nine-thousand rounds of subsonic ammunition for them.
Two of the rifles, with two-thousand rounds of ammunition, were delivered to the Aberdeen testing grounds for testing purposes in 1967. Aberdeen worked out several issues in the rifle, and reports from the LWL indicated that the rifle was delayed for deployment twice because of them.
Five of the rifles, along with most of the ammunition, were delivered to the 23rd Infantry Division of the United States Army in 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, particularly of the Super Grade African model, 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 integrally-silenced barrel, inspired by the De Lisle carbine, the weapon's firing signature would be inaudible beyond 100 meters.