Monday, 17 April 2017

British Explosive Ordnance - Army and Navy Demolition Stores

British Explosive Ordnance

Firing Devices and Demolition Stores


British firing devices, referred to as switches, are used to initiate booby traps or, in some cases, demolition charges.  Switches generally operate by pull, pressure, release of pressure, or various combinations of these actions.  Time or long-delay switches may utilize the corrosive reaction of acid with metal, or lead fatigue to achieve the delay.  Many types of improvised switches of both electrical and mechanical types may be constructed from common materials, but are not dealt with in this publication.

Demolition stores include the more common Detonators, primers, instantaneous fuze, safety fuse, detonating fuse, prepared demolition charges, and military explosives used by the British.  These stores are used chiefly in demolition work, or in the preparation of booby-trap charges.


Switches are ordinarily designated by the "type of action" (pull, pressure, etc.), a "Number" corresponding to the US Navy "Mark", and a Roman numeral "Mark" corresponding to the US Navy "Modification".

The designation of demolition stores varies with the particular item, but usually follows the common "Number" and "Mark" system.

Army Demolition Stores

Bangalore Torpedoes

2-inch Bangalore Torpedo Mks I and II: This torpedo, 62.5 inches long and weighing about 25 pounds, consists of a steel body fitted with an ogival hardwood head.  It contains a charge of about 7 pounds of Ammonal with  a Primer Mk II C.E. fitted at the front end.  Two studs are provided near the rear end of the body for assembly of the sections in series.  The body is painted service green or brown, with a red band, below which are located identification stencillings.  Two 1/4-inch buff bands enclose a 1-inch green band on which the letter "A" is stencilled to denote the Ammonal filling.

20-foot Lightweight E.P. Bangalore Torpedo: This torpedo is issued empty in sections 3-foot long and 3-inch in diameter.  It is made of light sheet steel.  Each section is split longitudinally down the center to form a top and bottom half-section.  A wooden nose plug, a wooden tail plug, six junction bands, and nine junction rings are issued with each outfit of seven complete sections of the torpedo.  The torpedo was originally designed to be used in conjunction with the 20-foot Flexible Torpedo, described below, as its filler, but it may be filled with cartridge-type explosive without any canvas lining.

20-foot Flexible E.P. Bangalore Torpedo: This torpedo consists of a 20-foot length of 2-inch diameter canvas hose, filled with "808", Gelignite, or Ammonal.  A double length of Cordtex, passing through regularly spaced primers, runs through the explosive-filled hose.  The torpedo was designed as an assault-demolition weapon to be used in single lengths, coiled, or bundled, or stretched out and tied to other lengths.  When rigidity is desired, this torpedo may be placed inside the 20-foot Lightweight Torpedo, described above.

1 and 1/2-inch Lightweight Bangalore Torpedo Mk I: This torpedo consists of a thin steel tube, 1 and 5/8-inches in diameter.  It is issued in two lengths, 6 feet and 10 feet.  The torpedo is painted brown, with a red band, below which identification stencillings are painted.  Two 1/4-inch buff bands enclose a 1-inch green band on which the letter "A" is stencilled to indicate the Ammonal filler.  An ogival wooden head, fastened to a short metal sleeve with screws, is provided with each set of four sections.  A studded metal band is provided with each section for use in joining the sections together.

Cavity Charges

Stock Charges: The 5-ounce Stock Demolition Charge Mk I and 7-ounce Stock Demolition Charge Mk II are exactly the same, except that the latter is 2 inches longer than the former.  The 5-ounce Charge Mk I is a small, linear cavity charge, consisting of a tin outer casing 6-inches x 1 and 5/16 inches x 2 inches, with an 80 degree angled copper arch fitted so that the apex is 1 and 3/8 inches above the base.  The charge is designed to cut 1-inch of steel.  Two Cordtex leads are led through a groove in the top of the charge, above a series of primer pellets, and are held in place by four straps soldered to the outer casing.  About 4 and 1/2-inches of the Cordtex project from either end of the charge as leads.  A 10-inch tinned copper wire is soldered to each corner of the charge to provide a method of fixing the charge, or of connecting two or more charges together.

Beehive Charges

6-inch Beehive Demolition Charge No.1 Mk III: The 6-inch Beehive No.1 Mk III is a 10 pound cavity charge containing 6 and 3/4 pounds of Pentolite.  The charge measures 6 inches in diameter and 7 inches in length, with three 4 and 1/2 inches legs attached to the base to give the proper stand-off distance.  An 80 degree sheet steel cone is fitted to give a cavity-charge effect.  A removable cap on top of the container covers a primer tube containing the primers into which the detonator is inserted.

From time to time, other sizes of Beehives have been used by the British Army, as follows:
-16-25 pound Demolition Charge No.6 Mk I
-30 pound H.C. Demolition Charge Mk I (Nesting)
-35-50 pound Demolition Charge No.7 Mk I
-60 pound Demolition Charge No.8 Mk I
-75 pound H.C. Demolition Charge No.4 Mk I

Arched Charges

25-pound Arched Demolition Charge No.2 Mk I (General Wade): This charge is an arched linear charge, containing 26 pounds of Pentolite.  The container is made of tin-plate, and measures 9 inches x 12 and 3/4 inches x 6 and 3/8 inches.  The container is semi-cylindrical, with a 2 and 1/4 inches radius arch fitted into the bottom to give the cavity-charge effect.  The charge is designed to be a general purpose charge, combining some of the advantages of the coned type of charge with those of the ordinary contact type.  It is thus adequate to effect serious damage against the majority of targets likely to be encountered by assault troops, i.e., against reinforced concrete and armor plate up to 2 inches in thickness.

26-pound Arched Demolition Charge (M.S. Shape): This charge is a slight adaptation of the General Wade.  The thickness of the explosive at the top has been reduced to 2 and 1/2 inches and the base pressure charge has been increased by about 50% giving the following dimensions, 9 inches x 17 inches x 5 inches.

Hayrick Charges

15-pound Hayrick Demolition Charge No.3 Mk I: The Hayrick charge is a linear cavity charge designed to cut the tension reinforcing bars of reinforced concrete structures.  It consists of a mild steel body containing the HE filling, with a blast plate fitted internally to provide the cavity-charge effect.  The body is rectangular in shape, measuring 11 and 1/4 inches x 6 inches x 17 and 1/2 inches.  One end is open and formed with flanged end plates, while the opposite end is shaped to an apex and carries two detonator sleeves, a sealing plate, and the fuze support.  About 15 pounds of Pentolite make up the HE filler, bringing the total weight to about 27.5 pounds.

Magnetized Charges

Clam Mk III: The Clam is a small time bomb with a magnetic base, which enables it to be attached instantly to any flat iron or steel surface, such as engine blocks, railroad tracks, steel plate, etc.

The body is a black plastic box with rounded corners, measuring 5 and 3/4 inches x 2 and 3/4 inches x 1 and 1/2 inches.  At each end of the box is a magnet compartment, in which the two magnets are loosely mounted so that they can grip an uneven surface.  The center compartment of the box contains about 8 ounces of the HE filler, usually Tetryl/TNT 45/55.  The box is closed by a flat lid held in place with four screws.

A standard L. Delay Switch No.9 Mk I, with a Detonator No.27 attached, serves as the delay initiator.  It slips into a groove in the top part of the body and is held in place by a small clip.

Limpet Mk III: The Limpet is a small, self-contained, delay-action mine with a magnetic base, which allows it to be fitted instantly to any iron or steel target, such as a tank or the hull of a ship.

The Limpet is designed to function either on land or under water, and carries a charge of 3 and 1/2 pounds of HE filler, usually Tetryl/TNT 45/55, which is sufficient to pierce 60mm plate.  Exceptionally powerful segmental magnets, flexibly mounted, allow it a firm grip even on uneven surfaces.  It will remain in place on the average vessel at speeds up to 16 knots.

The explosive container of the Limpet Mk III is a separate unit, which can be detached from the magnet ring so that the device can be used without magnets if desired.  This container weighs about 4 and 1/4 pounds filled.  The magnet ring weighs 5 and 1/4 pounds, bringing the total weight of the device to 9 and 1/2 pounds.  A carrying ring is fitted to the top of the limpet body.

A standard L. Delay Switch No.9 Mk I, with a Detonator No.8 attached, serves as the delay initiator.  It is inserted in a special holder, which gives a watertight joint when inserted int he magazine.

The earlier Limpet Mk II was fitted with two magazines, allowing the use of a duplicate igniter system to provide against possible failure.

Rigid Limpet: The British Rigid Limpet is designed for the destruction of tanks or other steel structures.  The device is painted field gray and consists of a rectangular box of sheet brass, 8 and 1/4 inches long x 2 and 1/2 inches wide x 2 and 1/2 inches deep.

The box contains a charge of 2.5 pounds of plastic HE, moulded to accept a detonator at each end.  A pair of brass brackets are riveted to either side of the brass body, and a brass rod is secured between each pair of brackets.  To each rod are fitted three permanent U-shaped magnets, each fastened by metal straps to a rubber mounting.  These magnets are retained in position by flanges on the rod.  The rubber mountings allow limited movement to the magnets, so that the Limpet can be readily attached to uneven surfaces.

An internally threaded brass cap provides a filling hole.  A threaded adapter fixed centrally to the brass filling cap and another threaded adapter fitted to the other end of the body provide means for inserting the AC Delay Igniter Mk I, with which the Limped is fuzed.

This initiating mechanism, used only with the Rigid Limpet, is a chemical-type long-delay device, consisting of a brass body containing a spring-loaded striker.  The head of this striker is sunk in a celluloid disc, retaining the striker under spring compression.

Immediately above the celluloid disc are located cotton wadding and a glass ampoule of solvent accommodated in an enlarged recess in the body.  The top of the body is threaded externally to receive a threaded cap.  Screwed into the center of the cap is a threaded spindle, which bears on a rubber sealing disc.  To the top of the spindle is attached a wing bolt to permit manual operation.  A safety pin pierces the threaded spindle and the cap, preventing the spindle from being screwed down as long as the pin is in place.
The device is put in operation by removing the safety pin and screwing down the threaded spindle, thus crushing the ampoule and allowing the solvent to saturate the cotton wadding and work on the celluloid disc.  Eventually the celluloid is sufficiently softened to release the striker, which is then forced by its spring into the detonator threaded to the lower end of the body.  Delay times can be varied by changing the solvent ampoule.  The color of the ampoule indicates the delay at 20 degrees Celsius.

 Dimensions and functioning details of the igniter follow:

Overall length: 5 and 1/2 inches
Detonator length: 4 and 1/2 inches
Body diameter: 1 inch

Delay at 20 degrees Celsius:
-Red ampoule: 4 hours
-Orange ampoule: 7 hours
-Yellow ampoule: 14 hours
-Green ampoule: 22.5 hours
-Blue ampoule: 36 hours
-Violet ampoule: 4.5 days

Delay times will increase at temperatures above 20 degrees Celsius, and decrease if temperatures are below that point.

Navy Demolition Stores

Explosive Charges

C.E./TNT Block Mk I

Explosive weight: 14 ounces
Length: 4 and 1/2 inches
Width: 2 and 1/4 inches
Height: 1 and 7/8 inches
Total weight: 14 ounces
Container: Metal
Remarks: May be made up into a 25-foot chain demolition charge

TNT Block Mk I

Explosive weight: 1.25 pounds
Length: 6 inches
Diameter: 2.4 inches
Total weight: 1.25 pounds
Container: Paper
Remarks: Usually inserted in a TNT Container Mk I, made of sheet steel

Amatol Charge Mk I

Explosive weight: 10 pounds
Length: 8.3 inches
Diameter: 6.5 inches
Total weight: 18.5 pounds
Container: Mild steel
Remarks: Receives one 4-ounce primer and a Detonator No.6

Amatol Charge Mk I

Explosive weight: 25 pounds
Length: 18.2 inches
Diameter: 6.6 inches
Total weight: 39.5 pounds
Container: Mild steel
Remarks: Receives two 4-ounce primers and No.6 detonators

Amatol Charge Mk II

Explosive weight: 25 pounds
Length: 18.5 inches
Diameter: 6.6 inches
Total weight: 41 pounds
Container: Mild steel
Remarks: Receives one 1 and 1/4 pound TNT block

Amatol Charge Mk I

Explosive weight: 50 pounds
Length: 18.5 inches
Diameter: 9 inches
Total weight: 70.5 pounds
Container: Mild steel
Remarks: Receives two 4-ounce primers and No.6 detonators

 In addition to these, heavy demolition is sometimes accomplished by adapting Depth Charges Mk VII, Mk VIII, Mk XI, and D Mks I and II, and Mine Charge Case Mk V for demolition firing.

Cavity Charges

5-pound RDX/TNT Cavity Demolition Charge Mk I: This charge is a liner cavity charge designed for cutting chain, steel wire rope, steel plate, etc.  The charge consists of approximately five pounds of 60/40 RDX/TNT.  The primer pocket will accept either a C.E. Primer Mk I, II, or III, or a 2-ounce Polar Blasting Gelatine Primer.  The charge has been designed for use with Briska Detonators No.6, and is not suitable for use with Detonators No.21 or No.25.  An I.C.I. Gasless Delay Detonator No.1 may be used when the charge is fitted with a C.E. Primer Mk III

The thin sheet-steel case encloses the water-tight cavity.  The case and primer-tube bung are watertight, allowing the charge to be used in depths up to three fathoms.  Two cleats and 6-foot lanyards attached ot the charge enable it to be quickly secured to its target.

Next Time: German Projectiles Introduction

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