Okla. Stat. tit. 21, § 1289.18

DEFINITIONS A. "Sawed-off shotgun" shall mean any firearm capable of discharging a series of projectiles of any material which may reasonably be expected to be able to cause lethal injury, with a barrel or barrels less than eighteen (18) inches in length, and using a combustible propellant charge, but does not include any weapon so designed with a barrel less than eighteen (18) inches in length, provided it has an overall length of twenty-six (26) inches or more. B. "Sawed-off rifle" shall mean any rifle having a barrel or barrels of less than sixteen (16) inches in length or any weapon made from a rifle (whether by alteration, modification, or otherwise) if such a weapon as modified has an overall length of less than twenty-six (26) inches in length, including the stock portion. C. Every person who knowingly has in his possession or under his immediate control a sawed-off shotgun or a sawed-off rifle, whether concealed or not, shall upon conviction be guilty of a Class D2 felony offense for the possession of such device, and shall be punishable by a fine not to exceed One Thousand Dollars ($1,000.00), or imprisonment as provided for in subsections B through F of Section 20O of this title, or both such fine and imprisonment. D. This section shall not apply to any firearm that is lawfully possessed under federal law or that is otherwise not regulated as a "firearm" pursuant to the National Firearms Act. E. The term "firearm" as used in this section and in the Oklahoma Firearms Act of 1971, shall not include an "antique firearm" as defined in 18 U.S.C., Section 921 (2006).