18 Pa.C.S. § 6111: Sale or transfer of firearms
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(c) Duty of other persons.--Any person who is not a licensed importer, manufacturer or dealer and who desires to sell or transfer a firearm to another unlicensed person shall do so only upon the place of business of a licensed importer, manufacturer, dealer or county sheriff's office, the latter of whom shall follow the procedure set forth in this section as if he were the seller of the firearm. The provisions of this section shall not apply to transfers between spouses or to transfers between a parent and child or to transfers between grandparent and grandchild.
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(f) Application of section.--
(1) For the purposes of this section only, except as provided by paragraph (2), "firearm" shall mean any weapon which is designed to or may readily be converted to expel any projectile by the action of an explosive or the frame or receiver of any such weapon.
(2) The provisions contained in subsections (a) and (c) shall only apply to pistols or revolvers with a barrel length of less than 15 inches, any shotgun with a barrel length of less than 18 inches, any rifle with a barrel length of less than 16 inches or any firearm with an overall length of less than 26 inches.