Need some opinions/ advice from some of you "gun hands"

The AR lower is what is considered the "firearm" by the ATF. The upper assemblies are not regulated and can be bought by anyone without going through an FFL. For a bolt action rifle, it is the receiver and for a semi-auto pistol or revolver, the frame assy. Generally the part that houses the trigger and/or firing mechanism, not the barrel, stock, etc.. Muzzleloaders and airguns are not considered firearms and thus don't require to be serialized and don't have to go through an FFL transfer and can be mail ordered and shipped direct in most states. The fact that they can be more powerful than many cartridge firing arms proves that the gov'ts logic is impeccable. That doesn't mean that they won't change their interpretation the next time the wind changes direction, it's happened before.