So I’m looking to build a 20 inch rifle and have most of the parts but have a couple questions on a few things. Any advise is greatly appreciated. I’m looking to end up with an old school looking rifle with a basic handguard and buttstock. Here’s a picture of what I have now. The basics are aero upper (fde) Aero upper parts kit Faxon 20 inch gunner barrel Psa bcg M4e1 lower Carbine buffer assembly What I think I need rifle length buffer assembly a2 F marked front sight post Basic rifle length plastic handguards A2 buttstock kit Question: Can I run a carbine buffer system with a barrel that has a rifle length gas system? Are all rifle length buffers the same?