I guess the guys at RedWolf Airsoft are impressed with this one which is also based on the WA GBB mech... "The Inokatsu M4 CQBR Masterwork Training Weapon, uses the WA M4 as a base model, transforming the already awesome gas blowback rifle, into something else entirely! All of Inokatsu's M4 MTW internals have been upgraded and reinforced to support higher power gases, from Top Gas to wait for it? 

That's right, CO2! Constructed out of Aluminum receiver and steel barrel, front sight, flash hider, with real material foregrip and stock, the Inokatsu M4 CQBR MTW is very robust and looks as realistic as a real gun. It sports a 5-positional retractable stock, a steel flash hider (QD), Steel Bolt Carrier and Bolt, Aluminum Hop-up Chamber, and a Real Type MK18 RIS unit. The Real Type MK18 RIS features KAC markings on the inside of the upper rail, just like the real steel versions, and is constructed completely from CNC aluminum.

The truly revolutionary system that Inokatsu employs is that all their MTW front sets are interchangeable for use on both the Marui AR-15 and the WA M4 series, with little to no modifications at all! The gun also uses real dimensions so all real gun accessories will fit onto this gun.

On Top Gas, the Inokatsu M4 CQBR MTW fires at 400fps with very strong blowback recoil. Using Red Gas, the CQBR shoots well over 400fps. However, the WA magazine is not as durable with RED GAS and will wear down much sooner than with TOP / GREEN gas.

Note that internal accessory and upgrade parts designed for the Western Arms M4 will fit the Inokatsu M4 as well. All parts on the Inokatsu M4 are the same design in dimensions as the Western Arms M4, except for the bolt and hop-up unit where Inokatsu has enhanced the design and is therefore no longer compatible with the Western Arms parts. But keep in mind that most parts designed for the WA M4 were meant to improve durability and performance with steel parts. Inokatsu's M4 internals are already 100% steel!"