This is a visitor’s SSK 300 Whisper Upper mounted on a Colt Match Target Pre-Ban AR-15. The silencer is a SSK unit and Dave advises that when using the silencer with 240-gr subsonic loads at 1050fps that the rifle sounds like a 0.30 caliber pellet gun. Supersonic 150-gr bullet loads are described as sounding like a .22
rimfire from the supersonic crack.
Note in the photo below that the silencer mounts over the barrel allowing a shorter overall length as opposed to a thread on silencer that mounts to the end of the barrel.
The Photo below shows the adjustment head of SSK's adjustable gas tube. Dave advises that this unit is an earlier SSK unit but that it has three distinct settings; high velocity, sub-sonic, off (requires manual charging).
The photo below gives proof that this upper has the right to be called a 300 Whisper as it is complete with SSK's markings and a 300 Whisper badge!
Special thanks to Dave for sharing his exceptional upper and the details above!