RBC-9 Roller Delayed Blowback, Belt-Fed, 9MM Carbine. Designed by @Nopel. Public Beta test version available here: https://odysee.com/@Nopel:6/RBC9_VersionB1:d
All parts made from hardware store stock and 3D printed or online retailers. Mine has a gun store bought AR9 barrel, but one can also make their own barrel.