I've got a pretty nice lower that's never been part of a rifle. Its a "caliber multi" as far as its marked. I bought it new and partially assembled, guy didn't have an upper for it yet. Those 8" 300 Blackout rifles are calling my name, but before I embark into NFA land I was wondering if anyone knows for sure the way I can tell if this lower can be legally built into a pistol. Does it have to be marked as a pistol? I've tried asking the local gunshop commandos, since they actually sell suppressors and other NFA items and gotten conflicting answers. My understanding is that a pistol can become a rifle (via SBR or really long barreled pistol) but going back again is less easy. So it boils down to, is this stripped AR lower somehow already a rifle or pistol? I have no interest in playing in the gray area here, so I am just wondering if it will be legal to build the lower into a pistol instead of a rifle as I originally planned. If this is illegal I'll probably either scrap the idea or go with a 16".