The Magpul PDR (Personal Defense Rifle) is a compact bullpup-style 5.56x45mm carbine being developed by Magpul Industries. Although halted in development, it has garnered some attention, largely due to its "futuristic" appearance. The system consists of a gas-operated bullpup intended to replace some submachine guns, M9 pistols and M4 carbines while still offering the rapid fire and range of a M4 carbine in an ultra compact firearm.
The PDR is one of the few personal defense weapons to use a standard caliber. This decision was made to minimize the logistic burden of the weapon. The method of operation is a short stroke gas piston that may or may not include a two baffle compensator, barrel lengths of between 10.5 to 12.5 inches. It is striker-fired, uses STANAG magazines, features an ambidextrous ejection system, and ambidextrous controls. A Picatinny rail offers mounting for various optics. There is also some indication of integrated lighting and/or laser systems. (From Wikipedia)