Hey guys, I'm considering buying a suppressor for my AR15 from a small local manufacturer. When I do this I'm gonna want to convert my 16" carbine upper to SBR, 9" or 10" (thoughts?). Can I just buy the barrel, tube, and block, apply for the stamp, and assemble it when the stamp comes back? Any good reasons to convert to piston drive while I've got it apart? Thanks in advance.