Autocannon · NATO
25x137mm NATO
The 25x137mm is a NATO-standardized Swiss autocannon round used in the Oerlikon KBA, M242 Bushmaster, GAU-12 Equalizer and GIAT M811..
- Caliber
- 0.9843″ · 25 mm
- Introduced
- 1970
- Case
- Rimless
- Primary use
- Military
- Status
- Active
- Introduced
- 1970
- Type
- Autocannon
- Origin
- Switzerland
- Inventor
- Oerlikon (approx: maker of record)
- Standard
- NATO
- Status
- Active
- Availability
- Not commercially available
- Case capacity
- 1073 gr H₂O
- Twist (typical)
- 1:24
- Primer
- Percussion (military)
- Case type
- Rimless
- Max pressure
- 45,000 psi, CIP transducer
- Eff. range
- 1500 yd
- Max range
- 4500 yd
- Recoil
- 1,346.7–1,388.5 ft·lb
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for 25x137mm NATO, so this is the shape gravity alone gives the advertised velocity. Drag would steepen it. The tool below solves real loads through their published G1 or G7 model.
Open in Ballistic Compare- Parent case
- —
Representative trajectory — modeled from a single velocity input (no published BC for this cartridge yet).
Dimensionscase measurements · scale drawing · size vs familiar rounds
Case dimensions — the scale drawing at the top of the page is built from these.
Wikipedia · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 25.00 | 0.984 | · |
| Neck ⌀ | 26.09 | 1.027 | |
| Shoulder ⌀ | 29.08 | 1.145 | |
| Shoulder angle | 24° | — | |
| Base ⌀ | 30.63 | 1.206 | |
| Rim ⌀ | 30.63 | 1.206 | |
| Belt ⌀ | n/a | ||
| Rim thickness | 3.13 | 0.123 | |
| Neck length | 25.81 | 1.016 | |
| Case length | 137.00 | 5.394 | |
| Overall length | 228.96 | 9.014 | |
Size vs familiar rounds
Drawn at true 1:1 — every case is accurate relative to the others. Absolute size depends on your screen's pixel density, so measuring one against a real ruler may be off. 25x137mm NATO is highlighted below.
Missing a dimension for 25x137mm NATO? Some case measurements aren't in a published SAAMI/CIP drawing yet. Have a factory or reamer print? Send it → — verified hard-to-find data earns a free Lindcott sticker.
Reloading costestimate cost per round vs factory
Estimate your cost per round and how it compares to factory. Inputs are yours — nothing is stored.
Cost estimate only — not load data. Charge weight is your input; follow published manuals for safe charges.
Connected reference
History
The 25x137mm is a NATO-standardized Swiss autocannon round used in the Oerlikon KBA, M242 Bushmaster, GAU-12 Equalizer and GIAT M811.
FAQs
- What twist rate does 25x137mm NATO use?
- 25x137mm NATO typically uses a 1:24 twist rate.
- What bullet diameter is 25x137mm NATO?
- 25x137mm NATO uses a 0.9843″ (25 mm) diameter bullet.
- Is 25x137mm NATO still in production?
- 25x137mm NATO is active; typical availability is not commercially available.
- What is 25x137mm NATO used for?
- 25x137mm NATO is primarily used for military.
Sources & provenance
Data & sources. Specs compiled from the Lindcott Armory reference; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →
