Quote History Quoted:
ive heard that a lower that is sold as a rifle lower cannot legally be used as a pistol but a lower sold as a pistol can be used as a rifle too, But i guess PSA sells them as a third option.
View Quote
They're all "other firearms", whether stripped or built. The box on the form doesn't change that fact. Think about it this way...if you bought an 870, or an AR-15, and the FFL incorrectly checked Handgun instead of Long Gun, what type of firearm do you now own?
Question 16. Type of Firearm(s): "Other" refers to frames, receivers and other firearms that are neither handguns nor long guns (rifles or shotguns), such as firearms having a pistol grip that expel a shotgun shell, or National Firearms Act (NFA) firearms, including silencers.
If a frame or receiver can only be made into a long gun (rifle or shotgun), it is still a frame or receiver not a handgun or long gun. However, frames and receivers are still "firearms" by definition, and subject to the same GCA limitations as any other firearms. See Section 921(a)(3)(B). Section 922(b)(1) makes it unlawful for a licensee to sell any firearm other than a shotgun or rifle to any person under the age of 21. Since a frame or receiver for a firearm, to include one that can only be made into a long gun, is a "firearm other than a shotgun or rifle," it cannot be transferred to anyone under the age of 21, nor can these firearms be transferred to anyone who is not a resident of the State where the transfer is to take place. Also, note that multiple sales forms are not required for frames or receivers of any firearms, or pistol grip shotguns, since they are not "pistols or revolvers" under Section 923(g)(3)(A).
Disclaimer: it's possible some states, like CA, may have local regulations that change the way it's handled.
ETA: if you change your question to "configured as a rifle" instead of "sold as a rifle lower", you have a valid point. But in order to be configured as a Handgun or Long Gun, it would've had to have an upper attached. It may be a po-tay-to po-tah-to situation, but there's not really any such thing as a pistol lower or rifle lower. There are, however, lowers with stocks and lowers with braces.