O
- Oberndorf Mauser Type B Pattern 80
- Objective Individual Combat Weapon
- OCSW
- Olin CAWS
- Olin/Winchester FAL
- Olympic Arms CAR-97
- Olympic Arms K23-B
- Olympic Arms OA-93
- Olympic Arms OA-93 TG
- Olympic Arms OA-96
- Olympic Arms PCR Service Match
- Omega SPS-12 (US - Semi-Automatic Shotgun - 12 Gauge)
- Orgullo De La Industria Argentina
- TALA (Argentina - Pistol - .22LR)
- Orita Model 1941
- Ortgies pistol
- OTs-01 Kobalt
- OTs-01S Kobalt
- OTs-11 Tiss (Russia - Assault Rifle - 9 × 39 mm)
- OTs-14 Groza (Russia - Assault Rifle - 9 × 39 mm)
- OTs-20 GNOM revolver
- OTs-23 DROTIK
- OTs-39 aka TsKIB SOO OTs-39
- Owen Machine Carbine (Australia - Submachine Gun - 9x19mm Parabellum)
Read more about this topic: List Of Firearms