Let's find out what L'Antre Du Dingo thinks of the Well Pro PPK20 GBB as he reviews it in this video. The WELL PRO PPK-20 SMG GBB Airsoft is a gas blowback submachine gun with a full metal receiver, a polymer handguard with top and bottom rails, and a railed dust cover for optic attachments. It features a 14mm CCW threaded outer barrel, a 155mm 6.04 inner barrel, and an adjustable folding stock. The magazine holds 38 rounds of gas.