Designation
20 × 102 mm HEI (M56A3)
Cartridge length
Maximum 168.02 mm
Cartridge mass
Approx. 258 g
Projectile mass
101 g
Velocity at 23.7 m
1,030 ± 15 m/s
Velocity standard deviation
Maximum 12.19 m/s
Mean pressure
Maximum 4,254 kg/cm²
Accuracy at 232.4 m
Maximum 16.15 cm
Bullet extraction force
499–1,179 kgf
Action time
Maximum 4 ms
Case
M103 · CuZn30 brass
Projectile shell
Steel · Ç 1040
Fuze / primer
M505A3 / M52A3B1 electrical primer
Propellant
Ball powder
Link type
M12 or M14
Compatible weapons
M39, M61 and M197