Overview
William Mills, a hand grenade designer from Sunderland, patented, developed and manufactured the "Mills bomb" at the Mills Munition Factory in Birmingham, England, in 1915. The Mills bomb was adopted by the British Army as its standard hand grenade in 1915, and designated as the No. 5. It was also used by the Irish Republican Army.
The Mills bomb underwent numerous modifications. The No. 23 was a variant of the No. 5 with a rodded base plug which allowed it to be fired from a rifle. This concept evolved further with the No. 36, a variant with a detachable base plate to allow use with a rifle discharger cup. The final variation of the Mills bomb, the No. 36M, was specially designed and waterproofed with shellac for use initially in the hot climate of Mesopotamia in 1917, but remained in production for many years. By 1918 the No. 5 and No. 23 were declared obsolete and the No. 36 (but not the 36M) followed in 1932.
The Mills was a classic design; a grooved cast iron "pineapple" with a central striker held by a close hand lever and secured with a pin. Although the segmented body helps to create fragments when the grenade explodes, according to Mills' notes the casing was grooved to make it easier to grip and not as an aid to fragmentation. The Mills was a defensive grenade: after throwing the user had to take cover immediately. A competent thrower could manage 15 metres (49 feet) with reasonable accuracy, but the grenade could throw lethal fragments farther than this. The British Home Guard were instructed that throwing range of the No. 36 was about 30 yards with a danger area of about 100 yds.
At first the grenade was fitted with a seven-second fuse, but during combat in the Battle of France in 1940 this delay proved too long—giving defenders time to escape the explosion, or even to throw the grenade back—and was reduced to four seconds.
The heavy, segmented bodies of "pineapple" type grenades result in an unpredictable pattern of fragmentation. After the Second World War Britain adopted grenades that contained segmented coiled wire in smooth metal casings. The No. 36M Mk.I remained the standard grenade of the British Armed Forces and was manufactured in the UK until 1972, when it was completely replaced by the L2 series. The 36M remained in service in some parts of the world such as India and Pakistan, where it was manufactured until the early 1980s. Mills bombs were still being used in combat as recently as 2004 e.g. the incident which killed US Marine Jason Dunham and wounded two of his comrades.
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