Colt SCW (Sub Compact Weapon) is a piston system 10.3" barrel with a new short bolt & short buffer tube and folding compact stock around 2010 - 2011.
Here's a quote from an AR15.com archive thread:
"The Colt SCW is the most compact of Colt's 5.56mm family of weapons. This personal defense weapon features a one-piece Monolithic upper receiver, with a Colt collapsible folding buttstock for close quarters battle. Where previous small caliber PDW's did not suffice for engaging objectives, the Colt SCW in 5.56x45 NATO allows for the stopping power soldiers need on the battlefield. Its ultra lightweight compact design provides maneuverability in the tightest of areas, and also caters to quick and easy transition from vehicles. Incorporating the ALP (Articulating Link Piston) in the SCW-P and a new bolt carrier/buffer system the SCW has been engineered to provide the same reliability as the Colt M4, but in a more compact design. Additional benefits include a reduction in recoil and an increase in controllability. Equipped with its holster/sling system, the Colt SCW allows for an easy transition from any other weapon of choice. Designed specifically for Vehicle & Aircraft Crews, Special Forces and Reconnaissance Units, the Colt SCW increases mobility and firepower on the modern battlefield with longer range acquisition and ease of handling. With all of these combinations of enhancement and augmentations, this weapon has won the right to its name "Colt SCW". For wherever a light, mobile, and trusted weapon is needed, Colt continues to stay at the forefront of its competitors with innovative & quality products that are still to be matched.
Caliber - 5.56x45 NATO
Weight: 6.5lbs
Overall Length: Extended - 30.25" Retracted - 28" Folded - 23.5"
Barrel Length: 10.3"
Bore: Hard chrome lined, 6 lands & grooves, 1:7 twist
Method of Operation: SCW - Direct Impingement
SCW-P - ALP (Articulating Link Piston)
Muzzle Velocity: 2,600 FPS
Effective Range: 400m
Front Sight: Adjustable Folding Front
Cyclic Rate of Fire: 700-950 rpm"
I had seen them in two versions a standard with KAC M4 RAS rails and a monolithic upper, Colt shown them at the 2010 and 2011 Shot Shows, check some YouTube vids.
Never seen any civilian models for sale ever since they shown them.
Here are some article links.
http://www.defensereview.com/colt-sub-compact-weapon-scw-folding-stock-tactical-556-sbr-photos/
http://www.guns.com/reviews/colt-scw/