JK Army does a test of the SP SYSTEM MWS Complete Gas Blowback Rifle at Pozi Shop. This incorporates all the upgrade parts from SP System for the Tokyo Marui MWS Gas Blowback System that includes Hop-Up, Bolt Carier Forward Assist, Magazine Spring, Mag Gas Gasket, Hop-Up Bucking, Nozzel Spring, and more. Check the video out of the upgrades are worth purchasing for your M4 MWS.