The standard cannon cartridge of American fighter aircraft for 70 years. Fires a 1,540-grain projectile at over 3,400 fps from the M61 Vulcan rotary cannon. Technically legal to own in most states as a rifle cartridge, though practically impossible to obtain commercially.
Type: Rifle
Introduced: 1956, United States
Parent case: None
Standardization: NATO
Bullet diameter: 0.787" (20 mm)
Case length: 4.016" (102 mm)
Overall length: 5.748" (146 mm)
Max pressure: 65,000 PSI
Rim type: Rimless
Primer: Electric Primer
Typical twist rate: 1:24
Muzzle velocity: 3300–3450 fps
Muzzle energy: 37200–40700 ft-lbs
Effective range: 2000 yd
Common bullet weights: 1540 gr
Primary use: Military, Anti-Aircraft, Air-to-Air
Production status: Active
Also known as: 20x102mm · 20mm M61 · 20mm PGU
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…
Notable firearms: M61 Vulcan (F-16, F-15, F/A-18), M163 VADS, Phalanx CIWS, M197 (AH-1 Cobra), GAU-12 Equalizer
Military use: {"country":"United States","years":"1956-present","conflicts":["Vietnam War","Gulf War","Iraq","Afghanistan","Various"]}, {"country":"NATO Forces","years":"1960s-present","conflicts":["Various"]}
Similar cartridges: .950 JDJ, 23mm Volkov-Yartsev