SB 23 (1999):
Characteristics Test

Senate Bill 23, authored by Senator Don Perata, was signed by Governor Gray Davis on July 19, 1999, and took effect on January 1, 2000.^[1] SB 23 expanded the Roberti-Roos Act by adding assault weapon definitions based on physical characteristics alongside the existing make-and-model definitions.

The Characteristics Test

SB 23 added what is now Penal Code Section 30515, which classifies a semiautomatic firearm as an assault weapon if it meets specific feature combinations:

• Semiautomatic centerfire rifle with detachable magazine plus any one of: pistol grip that protrudes conspicuously beneath the action, thumbhole stock, folding or telescoping stock, grenade or flare launcher, flash suppressor, or forward pistol grip
• Semiautomatic centerfire rifle with fixed magazine capacity exceeding 10 rounds
• Semiautomatic centerfire pistol with detachable magazine plus any one of: threaded barrel, second handgrip, barrel shroud, or capacity to accept a magazine outside the pistol grip
• Semiautomatic shotgun with both a folding or telescoping stock and a pistol grip protruding conspicuously beneath the action, thumbhole stock, or vertical handgrip, or a semiautomatic shotgun that does not have a fixed magazine

Registration Period

Owners of firearms meeting the new characteristics test definition were given until December 31, 2000, to register them with the DOJ as assault weapons.^[2] After registration closed, possession of unregistered firearms meeting the definition was generally prohibited, subject to statutory exceptions. Registered firearms are subject to the same restrictions as Roberti-Roos registered assault weapons.

Compliance Pathways

Because the characteristics test hinges on the combination of a detachable magazine plus prohibited features, two primary compliance strategies emerged:

• Featureless build: Remove all prohibited features (use a fin grip or Thordsen stock instead of a pistol grip, pin the stock, remove flash hider) while keeping a standard detachable magazine release. This approach preserves normal magazine changes but alters the ergonomics of the firearm.
• Fixed magazine: Install a magazine lock device that requires separation of the upper and lower receivers (or equivalent disassembly of the action) to release the magazine. This allows retention of all prohibited features but significantly slows magazine changes.

Bullet Button Era (2000-2016)

Former DOJ regulation Section 5469 defined a "detachable magazine" as an ammunition feeding device that could be removed readily without disassembling the firearm action or using a tool. A bullet or ammunition cartridge counted as a tool. The Bullet Button, a device requiring a bullet tip or small tool to press the magazine release, was initially accepted as making the magazine non-detachable. SB 880 and AB 1135 (2016) redefined "fixed magazine" to require disassembly of the firearm action. Beginning January 1, 2017, firearms with a tool-removable magazine and the specified features met the revised assault weapon definition, with a registration route and a conditional possession exemption for eligible prior owners.