This detonator safe, vane operated nose fuze fires instantaneously upon impact. Air travel of approximately 1,000 feet is required for the delay arming mechanism to arm the fuze. Mod 3 and Mod 4 are the same mechanically. Mod numbers merely indicate different manufacturers.
No information about functioning.
The explosive components consist of a detonator, an auxiliary booster lead, a booster lead, and a booster (tetryl, about 0.9 ounce, either pellet loaded or loaded in place). The booster screws into the fuze body and is held by the booster cover crimped into the groove provided.
Detonator Mk 21 Mod 0.
MIL-HDBK-146, Fuze Catalog (1982)
TM 9-1325-200, Bombs and Bomb Components (1966)
OP 2216, Volume 1 - Aircraft Bombs, Fuzes, and Associated Components (1960)
OP 1664, Volume 2 - US Explosive Ordnance (1947)
USNBD - Bombs and Fuzes, Pyrotechnics (1945)
TM 9-1904, Ammunition Inspection Guide (1944)