I'm new to firearms and just recently started my first AR15 build, dubbed "Project Muttley." I am nearly finished with this project, the only parts I need are barrel, hand guard, and buttstock. As I was researching barrels I got the itch to start another project, an AR Pistol in 5.56. I've read several articles about the rules surrounding AR pistols but I may be more confused now. My question is this: can I build both guns at the same time, or do I have to finish the rifle build before I purchase certain parts for the pistol build? I'm assuming the receivers are all safe to purchase, but can I have a short barrel or pistol buffer tube while my rifle build is in its current state? What is the best way to go about this? Sorry if this isn't the correct thread. Please move as appropriate.