25 mm caliber is a range of autocannon ammunition. It includes the NATO standardized Swiss 25×137mm, the Swiss 25×184mm, the Soviet 25x218mmSR, and the Chinese 25×183mmB.
The 25 mm round can be used for anti-materiel or anti-personnel purposes. In the anti-personnel role, a 25 mm weapon armed with HE rounds can kill large numbers of opposing troops either in the open or in light fortifications. In the anti-materiel role, a 25 mm weapon armed with armor-piercing rounds can disable many types of aircraft and ground vehicles, including some main battle tanks.
The US military uses 25 mm weapons in their AV-8B Harrier, AC-130 gunship, M2 Bradley, LAV-25, F-35 Lightning II and as a standard ship-based munition in the Mk 38 autocannon.
Several sub-types of the NATO 25 mm ammunition are available—the most common being armor-piercing, high-explosive, sabot, tracer, and practice rounds. Cartridges are usually composed of a combination of the aforementioned categories. For example, the M791 is an armor-piercing discarding sabot with tracer (APDS-T) round. It is used against lightly armored vehicles, self-propelled artillery, and aerial targets such as helicopters and slow-moving fixed-wing aircraft.
| Weapon | Country of origin | Designer | Cartridge | Type | |
|---|---|---|---|---|---|
| Oerlikon KBA |  Switzerland | Rheinmetall AG | 25×137mm | Autocannon | |
| M242 Bushmaster |  United States | Hughes Helicopters | 25×137mm | Chain gun | |
| GAU-12/22 Equalizer | United States | General Electric | 25×137mm | Rotary cannon | |
| GIAT M811 |  France | GIAT Industries | 25×137mm | Autocannon | |
| Oerlikon KBB | Switzerland | Rheinmetall AG | 25×184mm | Autocannon | |
| Oerlikon KBD | Switzerland | Rheinmetall AG | 25×184mm | Autocannon | |
| Type 61 |  China | 25×218mmSR | Anti-aircraft autocannon | ||
| Type 95 SPAAA | China | 25×183mmB | Anti-aircraft autocannon | ||
| ZPT-90 | China | 25×183mmB | Autocannon |
| Weapon | Country of origin | Designer | Cartridge | Type | |
|---|---|---|---|---|---|
| 25 mm Hotchkiss anti-aircraft gun/Type 96 25 mm AT/AA gun | France | Hotchkiss et Cie | 25×163mm | Anti-aircraft autocannon | |
| 25 mm Hotchkiss anti-tank gun | France | Hotchkiss et Cie | 25×193.5mmR | Anti-tank gun | |
| 25 mm M1940 anti-aircraft gun | Mikhail Loginov and Lev Loktev | 25×218mmSR | Anti-tank gun | ||
| 25 mm Bofors M/32 anti-aircraft gun |  Sweden | Bofors | 25x205mmR (initial) or 25x187mmR (later) | Anti-aircraft autocannon |