| Code Value | Definition |
|---|---|
| A | AUTOMATIC ACTION |
| B | BOLT ACTION |
| C | CARBINE |
| D | DERRINGER |
| E | DOUBLE-BARREL (SIDE-BY-SIDE) |
| F | FLARE |
| G | GAS OR AIR |
| H | FLINTLOCK |
| I | SEMIAUTOMATIC ACTION (AUTOLOADING) |
| J | JET-PROPELLED |
| K | BLANK |
| L | LEVER ACTION |
| N | LAUNCHER |
| O | OVER AND UNDER |
| P | PUMP ACTION |
| R | REVOLVER |
| S | SINGLE-SHOT |
| T | RECOILLESS |
| U | PERCUSSION (CAPLOCK) |
| V | TEAR GAS |
| W | THREE BARRELS |
| X | FOUR OR MORE BARRELS |