The UCP operated on the delayed-blowback operating principle. The external design of the UCP appears to have been borrowed from the HK P2000 pistol, and includes ambidextrous controls, interchangeable backstraps, and a MIL-STD-1913 Picatinny-type rail system for the attachment of accessories. Like the USP and P2000 series of pistols, the trigger mechanism is reported to have been modular and capable of different configurations. The UCP was designed to accept an extended, threaded barrel capable of accepting the attachment of a sound suppressor made by Brügger & Thomet. The design remained in the prototype phase , and had been reported as entering limited trials with the Bundeswehr. In July 2009, HK USA's president, Wayne Weber, indicated that the UCP project has been cancelled because "HK felt it did not provide adequate ballistics in handgun form."