S.C. Code § 16-23-250
The provisions of this article do not apply to the Army, Navy, or Air Force of the United States, the National Guard, and organizations authorized by law to purchase or receive machine guns, military firearms, or sawed-off shotguns or sawed-off rifles, from the United States or from this State and the members of these organizations. Any peace officer of the State or of a county or other political subdivision, state constable, member of the highway patrol, railway policeman or warden, superintendent, head keeper or deputy of a state prison, correction facility, workhouse, county jail, city jail, or other institution for the detention of persons convicted or accused of crime or held as witnesses in criminal cases or persons on duty in the postal service of the United States or a common carrier while transporting direct to a police department, military, or naval organization or person authorized by law to possess or use a machine gun, or sawed-off shotgun, or sawed-off rifle, may possess machine guns, or sawed-off shotguns, or sawed-off rifles, when required in the performance of their duties. The provisions of this section must not be construed to apply to machine guns, or sawed-off shotguns, or sawed-off rifles kept for display as relics and which are rendered harmless and not usable.
The provisions of this article do not apply to any manufacturer of machine guns or military firearms licensed pursuant to the provisions of 18 U. S. C. Section 921 et seq., any person authorized to possess these weapons by the United States Department of the Treasury, the Bureau of Alcohol, Tobacco and Firearms, or any other federal agency empowered to grant this authorization, any common or contract carrier transporting or shipping any machine gun or military firearm to or from the manufacturer if the transportation or shipment is not prohibited by federal law, or persons licensed pursuant to Section 23-31-370.
S.C. Code § 16-23-250