Its irrelevant whether the gun is a handgun or a longarm.
Absent some specific exceptions, an unlicensed individual cannot sell or transfer a firearm to another unlicensed individual across state lines. Doesn't matter if its a pistol or a rifle/shotgun. An FFL can receive a gun from an individual in another state and an FFL can sell a long gun to a resident of another state if the sale complies with the law of both states. Interstate transfers of firearms between two unlicensed individuals is forbidden. Longarms can be sold/transfered in many states without an FFL between residents of the same state and some states also allow FTF deals between residents of the same state for handguns. PA, however, only allows a non-FFL transfer between two PA residents for longarms.
18 USC 922(a) It shall be unlawful—
(1) for any person—
(A) except a licensed importer, licensed manufacturer, or licensed dealer, to engage in the business of importing, manufacturing, or dealing in firearms, or in the course of such business to ship, transport, or receive any firearm in interstate or foreign commerce.