• DODIC: MN88 • P/N (Part Number): 13023565 • NSN: 1375-01-567-3615
The M21 consists of a 500-foot (152.4 m) shock tube, one end of which contains a built-in initiator (primer) attached to the shot assembly (M81), and the other end is terminated by a non-electric explosive cap that detonates without delay (Delay 0). The minitube is wound onto a spool so that the end with the primer and attached shot assembly protrudes from the center of the spool by at least 24 inches (60 cm). The M81 shot assembly remains on the end of the spool after being tested for rotation at 1500 rpm along the axis. 1. Minitube (shock tube) - Made of plastic tubing with a thin layer of reactive mixture (HMX / aluminum powder) applied to the inner wall. - When triggered, it transmits a low-energy pulse similar to a "dust explosion". - Reaction propagation velocity approximately 6500 ft/s (2000 m/s). - Maximum minitube diameter in M21 is 0.105 in (≈2.67 mm). 2. Explosive cap (non-electric detonator) - Overall cap length: 2.25–2.35 in (≈57.15–59.69 mm). - Outer cap diameter: 0.230–0.241 in (≈5.84–6.12 mm). - Explosive composition (charge sequence): • Intermediate charge: Lead azide (Type I per MIL-L-3055 or RD-1333 per MIL-L-46225). • Main charge: RDX (Type I or II per MIL-DTL-398). 3. M81 Firing Assembly - Attached to one end of the mini-tube (where the initiator is mounted). - Provides initiation of the percussion tube during pulling (removal of the safety pin and actuation of the mechanism).
• DODIC: MN88 • P/N (Part Number): 13023565 • NSN: 1375-01-567-3615