British No. 68 Rifle Grenade

Article submitted by UXO Guest Author Rick Stauber. For more information on the UXO Guest Author program, click here.

The British prior to the start of WWII developed the No. 68 Rifle Grenade. It was initially introduced into the British military service around mid-1940 but by 1942 it was withdrawn from front line service and issued to Home Guard units. The Home Guard units were essentially civilian militias that were armed by the military to assist in the event the homeland was invaded. The No. 68 Rifle Grenade required the use of a special designed "discharge cup" that was fitted on the barrel of a Mk-III service rifle as shown in the image below.

There were four modifications that occurred with the No. 68 grenade, all of which involved minor modifications to the design of the grenade and changes to the explosive filler used in the grenade. One type of explosives authorized in the grenade was Lyddite, which is a form of picric acid. Other explosives used in the various modifications of the grenade included RDX, TNT, and Pentolite. One additional note, the Mk VI version of the No. 68 grenade was actually manufactured in the United States and supplied to the British.

Technical Data
Overall Length - 7-inches
Diameter - 2.5-inches
Total Weight - 1-lb 15.5-oz
Main Charge - RDX/BWX 91.9, Lyddite, C.E./TNT 30/70, or Pentolite
Net Explosive Weight - 5.5-oz

The No. 68 Rifle Grenade was a rudimentary shape charge with a basic design flaw. A quick review of the cut-away line drawing shown below indicates the lack of a standoff between the target and the detonation of the grenade. A standoff distance is needed in order to allow time (i.e., micro seconds) to allow for the proper development of an explosive jet to form. Without the standoff the jet does not fully form which results in minimal target penetration.

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