О боезапасе Як1 и Bf109F4. Глюк или...

[Пахомов]

The following text is taken from the U.S. War Department Technical Manual, TM-E 30-451: Handbook on German Military Forces published in March 1945

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g. 20-MM MACHINE GUN (M.G.151/20). (1) General description. This is the 20-mm version of the Mauser M.G.151 design. It is only slightly different from the 15-mm gun. Barrels of the 15-mm and 20-mm models are not interchangeable. This gun also is issued in an electrically fired version, with a spring-loaded contact instead of a firing pin. Two types of ground mounts exist for the M.G.151/20, and there is a self-propelled antiaircraft version on a half-track.

(2) Characteristics.

Caliber . . . . . 20 mm (0.791 inch).
Length over-all . . . . . 69.75 inches.
Weight (including electrical control) . . . . . 93.5 pounds.
Operation . . . . . Recoil.
Feed . . . . . Disintegrating metal link belt.
Cocking . . . . . Electrical.
Firing . . . . . Percussion (electrical solenoid, manually operated trigger).
Rate of fire:
Unsynchronized . . . . . AP, 800 rounds per minute.
HE, 750 rounds per minute.
Muzzle velocity:
HE Incendiary . . . . . 2,650 feet per second.
AP Incendiary and APHE . . . . . 2,300 feet per second.

(3) Ammunition. Projectiles fired in this gun include high explosive, incendiary tracer, armor-piercing incendiary, armor-piercing high explosive, and high explosive incendiary.

[Пахомов]

У Williams'a - 700-750 (зависит,естественно, от типа снаряда), насколько помню.