If you want a bullpup airsoft gun based a 50BMG gun, then this IWA 2022 - GM6 Lynx Semi Auto 50 BMG Bullpup featured by BB2K Airsoft may just be the one you want done. It looks like Bruce had an orgasm holding it... "There are things that you only experience once. In Germany to have the opportunity to pick up a GM6 Lynx. This dream came true at the Carpathia Global booth. The Gepárd M6 (GM6 Lynx) manufactured by the Hungarian company Sero International is a long recoil bullpup rifle with a rotating bolt, fed with a 5-round magazine. It can be used with both .50 BMG and 12.7x108mm. Its effective range is 2000 meters."