Hey all. I have one more stripped lower laying here. I bought it new from a dealer a few years back. have not done an ar pistol, and want to make sure I'm understanding things correctly. It is my understanding that you can build an ar pistol a long as the receiver has never been built into a rifle. You can then use a 7.5" upper legally as long as there is no stock. Is that correct? Anything else i should know prior to this build? I appreciate any input. Thanks.