OP 1665 - British Ordnance; Part 5 - Hand and Rifle Grenades; Chapter 4 - Smoke, Illuminating, and Incendiary Grenades: Smoke Hand Grenade, W.P., No. 81 Mk I (Service)

BRITISH EXPLOSIVE ORDNANCE

Part 5 - Chapter 4

Smoke, Illuminating, and Incendiary Grenades

Smoke Hand Grenade, W.P., No. 81 Mk I (Service)

Data

Over-all length	5.25 in.
Diameter	2.4 in.
Total weight	1½ lb.
Filling	W.P., and H.C. Smoke Mixture
Fuzing	Striker Mechanism No. 3 Mk I
Delay	2½ to 4 sec.
Color	Green
Markings	Standard

Description: The grenade is composed of two parts; a bursting white phosphorus component and a generator component. Both components are made of tin plate, and construction follows normal trade practice. They are cemented together immediately af-ter filling. The W.P. component is similar in construction to Grenade No. 80, but is shorter and contains about half a pound of W.P. It is initiated by means of Striker Mechanism No. 3 Mk I, which fires a Detonator No. 75 Mk II. The striker mechanism is screwed into a re-cess in the top of the W.P. component above a brass detonator tube. The adapter of the striker is cemented in position. The housing can be unscrewed for priming. This hous-ing carries the spring-loaded striker held back by the safety lever and safety pin. The adapter and housing castings are made of zinc-base alloy.

The Detonator No. 75 Mk II consists of a cap mounted in a die-cast cap chamber (si-milar to Detonator No. 35M) with a length of Safety Fuse No. 17 Mk I Bickford to which is crimped a Detonator No. 78. The generator component is filled with H.C. Smoke Mixture and is ignited by a primed cambric disc, which is ignited by the flash of the detonator. This component is screwed and cemented to the bottom of the W.P. component.

Operation: The grenade is primed by removal of the housing assembly, insertion of detonator, and reassembly of the striker mechanism. To function, the lever is held firmly against the grenade body and the safety pin removed. As soon as the grenade is thrown, the fly-off lever leaves the body of the grenade and the cap is struck. The detonator fires after a delay of 2½ to 4 seconds, producing an immediate burst of white phospho-rus. The smoke and incendiary effects are comparable with Grenade No. 77 Mk I, and the safety distance is a little greater. The generator component is ignited when the detona-tor bursts and attains fail emission before the phosphorus smoke is dissipated. Rapid smoke emission from the generator then follows for about 45 seconds.

Figure 247 – Smoke Hand Grenade, W.P., No. 81 Mk I