S. 597 — Age 21 Act

This section amends 18 U.S.C. 921(a), the definitions section of the Gun Control Act of 1968, by inserting definitions for "(31) semiautomatic pistol," meaning any repeating firearm other than a shotgun or rifle that uses energy from a firing cartridge to extract and chamber rounds and requires a separate trigger pull per cartridge; "(38) semiautomatic shotgun," similarly defined for shotguns; and "(39) semiautomatic assault weapon," encompassing semiautomatic rifles, pistols, and shotguns with specified features (e.g., pistol grip, forward grip, threaded barrel, barrel shroud, folding stock), fixed magazines over 10 rounds (rifles) or 5 rounds (shotguns) or ability to accept detachable magazines, rate-of-fire accelerators (e.g., bump stocks), revolving-cylinder shotguns, and enumerated models (e.g., AK-47 and AR-15 variants, Barrett .50-caliber rifles).