I've researched this as best I can, but I seem to be getting conflicting answers.

I've read that the ATF considers a stripped lower a "firearm." But, as you know, in PA, a PA resident can sell another PA resident a rifle or shotgun (but not a handgun) without going through an FFL transfer.

However, I was told by a local dealer that since a stripped lower can be converted to either a rifle or pistol (depending on the length of the barrel you install), it must go through an FFL transfer.

Does anyone know FOR SURE (100% certain) the answer to the question in my title. Assume that the buyer and seller are both PA residents (and no criminal background, etc.)

Thanks