The Model 607 was Colt’s first attempt at a carbine version of the AR-15 rifle, shortening both the barrel and stock. The action is identical to a standard AR, but the barrel is only 10 inches (254mm) long, and the stock uses a collapsing design unique to this model. Most examples used a small suppressor to reduce the very substantial concussion of such a short 5.56mm barrel down to more like that of a standard 20″ rifle. Production of the Model 607 was limited to only about 50 units, and they included substantial variation in details. This example has a flat side receiver, 3.5 inch moderator, and 3-position selector. Some included burst options, either with or without a full auto setting.
Experience with the Model 607 (including limited experimental use with the SEALs in Vietnam) led to further development of the carbine concept. The barrel was lengthened to 11.5 inches and the stock redesigned to the modern style of telescoping stock we recognize today. These would become the Model 609/610, the Colt Commando or CAR-15.