British heavy machine gun and aircraft cannon cartridge developed for the Vickers Class C heavy machine gun and later aircraft use. Semi-rimmed case for reliable feeding in aircraft and vehicle-mounted weapons.
Type: Rifle
Introduced: 1925, United Kingdom
Parent case: None
Standardization: None
Bullet diameter: 0.51" (12.95 mm)
Case length: 3.189" (81 mm)
Max pressure: 25,000 PSI
Rim type: Semi-Rimmed
Primer: Berdan Large Rifle
Typical twist rate: 1:15
Muzzle velocity: 2520–2640 fps
Muzzle energy: 9347–14518 ft-lbs
Effective range: 800 yd
Common bullet weights: 664, 938 gr
Primary use: Military, Anti-Materiel
Production status: Discontinued
Also known as: .5 Vickers · .5 BMG (British) · 12.7x81mm
History: Developed in the early 1920s for a new class of British heavy machine guns, adopted as the Vickers .5 Class C gun. Used in RAF aircraft and on naval vessels through WWII. The semi-rimmed case allowed reliable feeding in both belt and drum feed systems. Replaced post-WWII by .50 BMG (12.7x99mm) as NATO standardization aligned British forces with American ammunition. Original ammunition is…
Notable firearms: Vickers Class C HMG, Various WWII British aircraft
Military use: United Kingdom, British Commonwealth
Similar cartridges: .50 BMG, .55 Boys, 12.7x99mm NATO