OP 1665 - British Ordnance; Part 5 - Hand and Rifle Grenades; Chapter 4 - Smoke, Illuminating, and Incendiary Grenades: Signal and Illuminating Rifle Grenade Nos. 57, 58, 59, 60, 61, and 62 (Obsolescent)

BRITISH EXPLOSIVE ORDNANCE

Part 5 - Chapter 4

Smoke, Illuminating, and Incendiary Grenades

2.5-in. Signal and Illuminating Rifle Grenade Nos. 57, 58, 59, 60, 61, and 62 (Obsolescent)

Data

Grenade No. 57
Type of grenade	Illuminating
Number of stars	1
Burning time	5½ sec.
Total weight	1 lb. ½ oz.
Over-all length	2¾ in.
Color	Buff
Markings	Red star in a white circle
Grenade No. 58	Green
Type of grenade	Illuminating with parachute
Number of stars	1
Burning time	28 sec.
Total weight	1 lb. 7 oz.
Over-all length	5 in.
Color	Buff
Markings	Red star in a white circle
Grenade No. 59
Type of grenade	Day signal
Number of stars	12 red, or 12 green, or combination
Burning time	7 sec. approx.
Total weight	1½ lb.
Over-all length	3½ in.
Color	Buff
Markings	Colored or parti-colored triangle to indicate star colors; "M" stencilled on triangle
Grenade No. 60
Type of grenade	Night signal
Number of stars	12 red, or 12 green, or combination
Burning time	11½ sec., red; 8 sec., green
Total weight	1½ lb.
Over-all length	3½ in.
Color	Buff
Markings	Colored or parti-colored disc to indicate star colors; "M" stencilled on disc
Grenade No. 61
Type of grenade	Day signal with parachute
Number of stars	3 red, or 3 green, or combination
Burning time	25 sec., red; 20 sec., green
Total weight	1 lb. 4½ oz.
Over-all length	5½ in.
Color	Buff
Markings	Three colored triangles to indicate star color
Grenade No. 62
Type of grenade	Night signal with parachute
Number of stars	3 red, or 3 green, or combination
Burning time	12 sec., red; 19 sec., green
Total weight	1 lb. 4½ oz.
Over-all length	5½ in.
Color	Buff
Markings	Three colored discs to indicate star color

Description: The construction of this entire series of grenades is generally similar to that of the 2.5-in. Illuminating Rifle Grenade No. 57 Mk I, whose description follows.

The body of the grenade consists of a cylindrical steel case, whose base is closed by a steel base plate. The top of the body is closed by several millboard discs. A friction-fit steel lid, with a ring for easy removal, fits over the base to protect the ignition system.

The base plate of the grenade has a drilled radial hole, which contains the ignition system. A small hole connected to its outer end allows the flash of the cartridge to con-tact the ignition system, while a coned hole at its inner end leads to the gunpowder burster in the interior of the grenade. The ignition system, which is retained in the radial hole by a screwed plug, consists of a tube of primed cotton cambric, a layer of gunpow-der, a delay pellet, and another small charge of gunpowder, which relays the flash to the gunpowder burster of the grenade. The paper-wrapped star rests on a millboard disc, which separates it from the gunpowder burster. The star composition is ignited by a layer of priming composition, in turn ignited by a small charge of sulphurless gunpowder; all of which are integral components of the star.

Operations: The base lid is removed grenade inserted into the discharger cup base-first. On firing, the propellant gases initiate the ignition system of the grenade and pro-pel it into the air. The delay allows the grenade to reach a hight of approximately 250 ft. before the burster ejects and ignites the star.

Remarks: These grenades are used in the 2½-in. discharger cup and fired by means of the 0.303-in. H. Rfile Grenade Cartridge Mk IZ. The 2-inch mortar signal and illuminat-ing bombs have largely replaced this series.

Figure 250 – 2.5-in. Illuminationg Rifle Grenade No. 57 Mk I