Rifle · NATO
20mm Vulcan
The standard cannon cartridge of American fighter aircraft for 70 years.
- Caliber
- 0.7874″ · 20 mm
- Introduced
- 1956
- Case
- Rimless
- Primary use
- Military, Anti-Aircraft, Air-to-Air
- Status
- Active
- Introduced
- 1956
- Type
- Rifle
- Origin
- United States
- Inventor
- General Electric / U.S. Ordnance
- Manufacturer
- General Dynamics Ordnance and Tactical Systems
- Standard
- NATO
- Status
- Active
- Availability
- Restricted
- Case capacity
- 400 gr H₂O
- Twist (typical)
- 1:24
- Primer
- Electric Primer
- Case type
- Rimless
- Max pressure
- 65,000 psi
- Eff. range
- 2000 yd
- Max range
- 6000 yd
- Recoil
- 150–200 ft·lb
Ballistics
Velocity only, no drag model: no published ballistic coefficient is on file for 20mm Vulcan, 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.
SAAMI · approximate| Measure | mm | in | ✓ |
|---|---|---|---|
| Bullet ⌀ | 20.00 | 0.787 | · |
| Neck ⌀ | 21.08 | 0.830 | ~ |
| Shoulder ⌀ | 26.67 | 1.050 | ~ |
| Shoulder angle | — | — | |
| Base ⌀ | 29.21 | 1.150 | ~ |
| Rim ⌀ | 29.50 | 1.161 | · |
| Belt ⌀ | n/a | ||
| Rim thickness | — | — | |
| Neck length | — | — | |
| Case length | 102.00 | 4.016 | · |
| Overall length | 168.00 | 6.614 | ~ |
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. 20mm Vulcan is highlighted below.
Missing a dimension for 20mm Vulcan? 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.
Firearms chambered in 20mm Vulcan
1 model in the database chamber 20mm Vulcan. Browse all →
Connected reference
History
Developed as the primary armament for post-WWII jet fighters, replacing .50 BMG as aircraft speeds made rifle-caliber guns insufficiently destructive. The M61 Vulcan cannon fires this cartridge at 6,000 rounds per minute from a six-barrel rotating mechanism — meaning a one-second burst delivers 100 rounds of 20mm projectiles. Armed virtually every American combat aircraft from the F-104 Starfighter through the F-22 Raptor and F-35. Ground variants arm the M163 VADS air defense system and the Phalanx CIWS naval close-in weapon system. The cartridge is technically a sporting cartridge under ATF rules if the projectile is not classified as explosive or incendiary — civilians can legally own 20mm Vulcan cases and inert projectiles, and a handful of civilians have built single-shot 20mm rifles. In practice, obtaining live military ammunition is essentially impossible without government contracts.
FAQs
- What twist rate does 20mm Vulcan use?
- 20mm Vulcan typically uses a 1:24 twist rate.
- What bullet diameter is 20mm Vulcan?
- 20mm Vulcan uses a 0.7874″ (20 mm) diameter bullet.
- Is 20mm Vulcan still in production?
- 20mm Vulcan is active; typical availability is restricted.
- What is 20mm Vulcan used for?
- 20mm Vulcan is primarily used for military, anti-aircraft, air-to-air.
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 →