ARMY - Chapter Eight Explosive Breaching

CHAPTER 8

EXPLOSIVE BREACHING

NOTE: Safety precautions regarding the procedures outlined in this chapter can be found in Chapter 9 (Breaching Safety) of this guidebook.

8.1 General. Intimate knowledge of explosives and associated equipment is a must for the explosive breacher. This knowledge gives the breacher the capability to provide the assault team with a successful explosive breach. The following paragraphs present an overview of explosives, initiators, and accessories and discuss various ways in which the behavior of explosives can be altered to achieve a successful breach.

8.2 Composition/Behavior of Chemical Explosives. An explosive is essentially a chemically unstable material, which produces an explosion or detonation by means of a very rapid, self-propagating transformation of the material into more stable substances. The transformation always liberates heat, forms gases, and propagates shock and loud noise.

The primary requisite of a chemical explosive is that it contains enough oxygen to initiate and sustain extremely rapid combustion. The surrounding air normally cannot supply enough oxygen by itself; therefore, sources of oxygen are incorporated into the combustible elements of the explosive. They can also be included by adding other substances in a mixture. These sources of oxygen are called oxidizers.

8.2.1 Explosive Mixtures. Explosive mixtures are mechanically blended, much like making a cake batter. The combustible and oxidizer are mingled together from separate ingredients. For example, black powder is a mechanical mixture of charcoal, sulfur, and niter (potassium or sodium nitrate) with water used as a bonding agent to form a paste. When the paste dries, it can be broken into pieces and ground into powder form for use. Most mechanically blended mixtures are classified as low explosives or propellants.

8.2.2 Explosive Compounds. Explosive compounds molecularly blend the combustible and oxidizer together. An example of a molecularly blended explosive is nitroglycerin. Glycerin is slowly poured into nitric acid where a chemical reaction occurs forming a new compound. Where physical mixtures are usually low explosives, chemical compounds are high explosives.

8.2.3 Low Exp1osives. Low explosives are said to deflagrate (burn) rather than detonate (explode). In doing so, they produce a pushing effect rather than a shattering effect. Primarily used as propellants, the mechanically mixed low explosive charge reduces the danger of bursting inside a weapon. Burning is transmitted from one grain to another producing gases that rapidly build up internal pressure for pushing a projectile through and out the weapon barrel.

8.2.4 High Explosives. Designed to shatter and destroy, high explosives have detonation velocities extending from 3,300 fps (ammonium nitrate) to 29,900 fps HMX (cyclotetramethylene tetranitrate). They differ from low explosives in that they usually must be initiated by the concentrated shock generated by a blasting cap or other priming system. This initiating shock sets up a “wave” which resonates through the explosive compound. The shockwave breaks apart the molecular bonds of the combustible material and oxidizer, releasing tremendous heat energy and rapidly expanding gases, all in a fraction of a second.

8.2.5 Explosive Work. The varying detonating velocities of explosives determine the type of work performed. Low explosives push or heave objects while high explosives shatter or break up objects. The breacher therefore selects an explosive based on the type of work or effect required for a specific target. A characteristic of explosives also related to work performance is that directional forces given off by a detonating explosive are at a 90 degree angle from the surface of that explosive. If, therefore, it is cut or shaped to provide 90 degree surfaces along a predetermined plane, the force of such a charge can be focused directionally with greater effect, ounce for ounce, than the same amount of explosive employed as a mass. Figure 8—1 illustrates the relationship of a shaped charge effect to a block charge effect.

8.2.6 Shaped Charges. The improved effectiveness of a shaped charge is caused by the so called Monroe Effect. When the detonator is fired, the detonation wave propagates through the explosive used. The detonation front reaches the conical liner, and the liner is subjected to the intense pressure of the front and begins to collapse. The cone collapses from apex to base under the point of initiation of the high explosive. The apex region has collapsed and collided on the axis of symmetry. This collision results in liner material under very high pressure being extruded along the axis of symmetry. This extruded material is called the jet. When the pressure exceeds the yield strength of the liner material, the liner behaves like a non-compressible fluid. About 10 to 20 percent of the liner goes into the jet; the remainder of the liner goes into the slug. The tip of the jet moves with a velocity of 29500 fps, and the slug has a velocity of 1000-2600 fps. This process performs much like the flame of a cutting torch penetrating a target like a hot knife cutting through butter. Figure 8-2 illustrates the step by step formation of a shaped charge jet. Shaped charges represent an advance in the employment of explosives for accomplishing specific work. Two basic types of shaped charge containers are available, the conical shaped charge and the linear shaped charge. Both are depicted in figure 8-3. Conical shaped charges are especially effective in punching holes in steel, concrete, and other materials. Linear shaped charges are used to cut or slice a target.

Figure 8-2. Shaped Jet Charge Formation

Figure 8-3. Shaped Charge Containers

Certain factors affect the penetrating/cutting efficiency and functioning of all shaped charges:

Cone Angle: The angle of the walls of the charge cone determine the speed and density of the jet. Angles vary between 30 and 80 degrees for most conical shaped charges.

Standoff: To achieve optimum penetration, the jet requires some air space to properly form. The shaped charge is placed at some predetermined distance from the target. This “standoff distance” is usually about one and a half times the diameter of the cone.

Liners: Penetrating efficiency is also enhanced by using lining materials such as steel, copper, or glass on the surface of the shaped charge. Such materials raise the jet temperature and add fine particles to the jet which act as an abrasive to assist cutting.

8.2.7 Explosively Formed Penetrators (EFP). EFPs operate using what is known as the Miznay-Shardin effect. They are lower velocity devices compared to shaped charges and have a tip velocity in the 3,930 - 9,840 fps range. However, they generate larger diameter, high mass projectiles and produce large holes in the target material. The penetration does not diminish rapidly over along stand-off distance if the projectile is aerodynamically stable. Air drag and tumbling are the main causes of degradation of stand-off. A minimum stand-off distance of about 1.5 charge diameter is required since the penetrator must have the time to form. Optimum performance is within 2-50 charge diameters. Figure 8-4 depicts the formation of the EFP.

Figure 8-4. Explosively Formed Penetrators

8.2.7.1 Flying Plate. A simplified and easy to fabricate version of an EFP is the Flying Plate. It was developed to penetrate steel and concrete targets. The flying plate is made of copper

and consists of a concave liner that has the shape of a section of a sphere. The wall thickness is uniform and varies from about 1.2 to 4 percent of the charge diameter, and the radius of curvature is constant which greatly simplifies and reduces the cost of the manufacturing process. Figure 8—5 shows a schematic of the plate with explosive charge.

The plate is backed by a thin layer of rubber to attenuate the shock wave. The explosive charge is placed behind the rubber layer. Plastic explosive is hand packed behind the plate. The explosive charge is centrally initiated with an electric or non— electric detonator or with det cord. Upon initiation, the center of the plate moves forward while the outside edge is stationary. After traveling a distance of about 1.5 - 2.0 plate diameters, the plate becomes convex and finally assumes the shape of a hollow cylinder with a hemispherical nose. The velocity of the flying p1~adapinnds on the composition of the explosive charge, the ratio C/K (C. - mass of explosive charge, M = mass of metal liner), and ezpltv. charge of L/D ratio (L = length of explosive charge, D = diameter of explosive charge). The metal plate and explosive charge are assembled in a PVC casing and are fired from a tripod. An aiming device is used to hit point targets.

Figure 8-5. Schematic of Flying Plate

8.2.7.2 Recommendations for Using the Flying Plate. The flying plate has been extensively tested by various military organizations in this country. From the test results, the following conclusions were drawn about performance of the flying plates against several targets.

Most commonly encountered targets:

Rolled homogeneous armor (RHA) Concrete Reinforced concrete

Recommendations:

Know your target Select proper C/M ratio

The C/M ratio:

When attacking RHA targets up to 1.5” thick; C/M = 2.0.

For RHA targets ~ - 6.0” thick, use C/N = 3.0 or 4.0.

When attacking concrete structures up to 20 inches, a C/M of 1.0 is sufficient.

For concrete structures with rebars up to 60 inches thick, use C/N = 2.0.

What damage to expect:

The depth of penetration (P) for RHA is:

D/3 < P < D/2

Where D = plate diameter

E.g., a 4” diameter plate will perforate a 1” thick RHA, but don’t expect it to pass through 4” thick armor. If a hole is to be made through 3 - 4” RHA, use a 6”, 8” or 10” plate.

The depth of penetration (P) for concrete is:

2 D < P< SD

E.g., a 10” plate will perforate at least 20” of concrete, but most likely will not go through 50” of concrete.

The depth of penetration (P) for reinforced concrete, which depends on the number of rebars, in most cases is:

D<P<2D

Eg., a 10” plate will perforate up to 10” of reinforced concrete, but will not go through 20” of reinforced concrete. However, one may expect to have a large amount of spalling back from the wall.

The hole size D(h):

The hole size depends upon the target material, standoff distance, and plate diameter.

For RHA D(h) - (0.4-0.7)DFor concrete D(h) = (1.0-2.0)DFor reinforced concrete D(h) = (1.0-1.5)D

Standoff distance: Plates with C/N = 1.0 were fired at targets from a standoff distance up to 300 feet. However, consistent target penetration was achieved at a standoff distance of 200 feet or less. To determine maximum standoff with consistent accuracy, multiply 10 ft by the diameter (i.e., for a 6 in. plate multiply 6 x 10 = 60 ft).

8.2.8 Explosive Trains. An explosive train is a series of explosions specifically arranged to produce a desired outcome, usually the most effective detonation of a particular explosive. Simple trains require only two steps, but some complex military munition trains have four or five more steps before terminating in a detonation.

The number of steps is a function of the sensitivity of the explosives involved. Sensitivity refers to the amount of external force needed to cause detonation. This sensitivity stems from an explosive’s ability to be initiated by shock, friction, flame, heat or a combination of these. Explosive sensitivity considerations divide these compounds into two categories, primary and

secondary explosives. Primary explosives are the most sensitive and are used to initiate the more insensitive or secondary explosive compounds. Explosive trains are classified as low or high based on the classification of the final explosive material in the train. The two step train has one primary and one secondary explosive as shown in figure 8-6.

Low Explosive Trains: The majority of low explosives require only a two step train. For example, a round of small arms ammunition uses a simple percussion primer and a propellant firing pin into a flame that ignites the propellant. The rapidly generated gases expel the bullet out through the core of the weapon.

High Explosive Trains: The nature of high explosive trains is affected by the wide range of sensitivity within the category of high explosive compounds. Many are three step trains consisting of a detonator, booster, and a main charge. A booster is a secondary explosive that provides amplification of the shockwave set off by the detonator, a primary explosive. This “boosted” shockwave detonates the less sensitive main charge. The basic three-step train is depicted in figure 8-7. An example of a four-step train is illustrated in figure 8-8.

Figure 8-6. Two Step Train

around main breaching charges. Success or failure of a demolition charge rests in the knowledge and abilities of the breacher to build a 100 percent reliable priming system.

All explosives must be acted upon by one or more of the following three physical actions before an explosion or detonation occurs.

Heat Shock Friction

As previously discussed, main charge explosives are normally too insensitive to detonate without the aid of a more sensitive initiating explosive called a primer, e.g., blasting caps or shock tube, etc. The following is a discussion of various types of priming systems.

8.3.1 Blasting Caps. Blasting caps are used for initiating high explosives. They contain small amounts of sensitive primary explosives. Although manufactured to absorb a reasonable amount of abuse under normal circumstances, blasting caps must be protected from unnecessary shock, heat, impact, or rough handling which might cause accidental detonation. When not in use,’ keep blasting caps in the protective carrying case as issued; never carry them loose in a pocket. Blasting caps are initiated either electrically or nonelectrically.

Electric Blasting Caps: As illustrated in figure 8-9, an electric cap is constructed from a small metal tube that is closed at one end. It contains an ignition charge, an intermediate charge, and a base charge. Two plastic insulated lead or leg wires, an insulated plug, and a small diameter corrosion resistant bridge wire across the leg wires constitute the electrical firing element. This assembly is crimped into the blasting cap tube.

Figure 8-9. Electric Blasting Cap

An electric current applied to the leg wires heats the bridge wire to incandescence which in turn kindles the extremely sensitive ignition charge. The resulting heat and flame sets off the intermediate charge and subsequently detonates the base charge. Electric current is usually supplied by a blasting machine. Base charges in electric caps are either PETN (pentaerythritol tetranitrate) or RDX (cyclotrimethylene trinitramine).

Nonelectric Blasting Caps. The construction and functioning of a nonelectric blasting cap is similar to that of an electric blasting cap except that it has no electric firing element. It has the same tubular metal construction and contains the same three detonating charge series. The ignition charge, however, is set off using the spit of flame provided by a burning safety (time) fuse inserted and crimped into the cap well. Figure 8-10 portrays a military nonelectric blasting cap.

Figure 8-10. Nonelectric Blasting Caps

8.3.2 Shock Tube. See figure 8-11.

8.3.2.1 Description. Shock tube is designed to carry a flame from the firing device to the explosive charge. It is the most widely used primer in the breaching community. The primary advantage is that it has the control of an electric system with the safety of a nonelectric system. The primary disadvantage is that the user requires specialized training; however, its use is easy to master.

8.3.2.2 Breaching Use. Shock tube is used in charge initiation. It is most often employed in a priming system with the MK54 mod 0 dual Firing Device found in the Pioneer Demo Kit. Othercommon military firing devices, such as the M81 fuse igniter, Ml42 firing device, or the MK55 Mod 0 handheld firing device (pen flare) may be used to ignite shock tube with adapters.

Figure 8-11. Shock Tube

8.3.2.3 Construction. A shock tube is a continuous core of HMX (cyclotetramethylene tetranitrate) dust (1 lb per 100,000 ft) encased in a polymer tube fitted on one end with a

nonelectric blasting cap containing 13.5 grains of RDX (cyclotrimethylene trinitramine) explosive as a base charge.

8.3.2.4 Characteristics

Size. Shock tube is available in the ammunition supply system. Existing stock of single lead instantaneous shock tube is being exhausted and replaced with the dual lead, OD green shock tube. on 50 ft spools. Yellow shock tube has a built in delay of 3.8 seconds. There will also be a tag on the tube stating the cap strength and delay time.

RE Factor. 1.50.

Color. . OD green (Other colors may be found until depleted.) Explosive core is white/ gray.

Water Resistance. Excellent.

Packaging. Shock tube is packaged eight spools per container and issued individually from stock when required. single 3.8 second delay is issued individually.

DODIC. The DODIC’s for shock tube are:

NM56 - Dual Instantaneous, 100 ftNMX1 - Single 3.8 second delay, 6 ft

Lona and Short Adapters. See figure 8-12.

Figure 8-12. Brass Adapter

8.3.3.1 Description. Brass adapters are used to adapt shock tube to the standard M81 igniter, M142, and the MX54 Mod 0 firing devices.

8.3.3.2 Construction. Brass adapters are of three piece brass construction. The shock tube receiving end is cone shaped and has a threaded, knurled knob to secure the shock tube. The longer end is made to adapt to the different initiation devices. There is a hole in the knurled portion of the main body assembly to allow venting. Both adapters are identical in appearance except that the long adapter has a longer set of threads that allow it to fit deeper into the body of the M81 fuse igniter allowing the igniter to be recocked.

8.3.4 Military Time Fuse M700. See figure 8—13. Military time fuse is normally used to detonate explosives nonelectrically. Most often, its purpose is to transmit a flame at a continuous and uniform rate to a nonelectric blasting cap. Black powder is widely used as the core burning powder because its burning rate can be easily regulated during manufacture. Time fuse is designed to have either a 30 or 40 second per foot burning rate (a 10 percent variation is allowable). Doctrine requires that safety fuse be tested to determine its exact burning time before use in any field operation.

Figure 8-13. Military Time Fuse M700

Military time fuse M700 has a dark green plastic cover with single yellow bands at 12 or 18 inch intervals and double yellow bands at 60 and 90 inch intervals. This it is illustrated in figure 8-13.

8.3.5 M60 Fuse Igniter. See figure 8-14.

Figure 8-14. M81 Fuse Igniter

8.3.5.1 Description. The M81 fuse igniter is used to ignite time fuses. When fitted with a brass adapter or silicone adaptor, it can be used to initiate the shock tube. The M81 igniter has a recocking feature in case of misfire.

8.3.5.2 Breaching Uses . The igniter is used in shock tube initiation.

8.3.5.3 Construction~ The outside is made of plastic. The igniter consists of the firing assembly, fuse holder assembly, and primer base assembly. The primer is a M209 shotgun primer and is used to ignite time fuses and shock tube.


Size. Approximately 4.78 in. lg and 0.75 in. dia.

RE Factor. NA.

Color. OD Green with yellow markings.


Packaging. Packed five per cardboard box with six cardboard boxes per amino can. The unit of issue is EA.

DODIC. The DODIC for the M81 fuse igniter is:

M766 - Igniter, Time Blasting Fuse, M81

8.3.6 M142 Multipurpose Demolition Firing Device. See figure 8-15.

Figure 8-15. M142 Multipurpose Demolition Firing Device

8.2.6.1 Description. The M142 is for use with anti—personnel land mines and for setting up booby traps using demolition charges. It has a four-mode capability; pressure, pull, pressure release, and tension release. The Ml42 can also be used to set off blasting caps or time blasting fuse.

8.3.6.2 Breaching Use. The primary use for breaching is as an initiator.

8.3.6.3 Construction. The device is made of plastic. The only explosive (M42 Primer), which is an explosive initiating element, is located in the coupling.

8.3.6.4 Characteristics. The basic component of the M142 is a mechanical switch designed for mechanical actuation by pressure, pull, pressure release, or tension release.

Color. The M142 is olive drab with yellow markings.

Water Resistance. The firing device is weather sealed and will function under water.

Packaging. The firing device is packaged 14 per box with 4 boxes (56 devices) per wooden crate.

DODIC. The DODIC for the M142 firing device is:

MLO3.- M142, Firing Device, Multipurpose

8.3.7 MKS5 Mod 0 Firing Device. See figure 8-16.

Figure 8-16. M7K55 Mod 0 Firing Device

8.3.7.1 Description. The MK55 Mod 0 is a firing device intended for use as a signaling device. It is commonly referred to as a pen flare.

8.2.7.2 Breaching Use. The primary use for breaching is as an initiator.

8.3.7.3 Construction. The device consists of an aluminum cylinder containing a spring launched trigger.


Color. Aluminum, brass or black in color.

Water Resistance. Waterproof to a depth of 200 ft.

Packaging. The firing device is individually sealed in a waterproof bag with 25 devices packaged per fiberboard box.

DODIC. The DODIC for the MKS5 Mod 0 firing device is:

MN12 — MK55 Mod 0 Firing Device

8.4 Main Charges. Most main charge explosives made for military use are designed to shatter and destroy. They must have high detonation rates and, because of combat conditions, must be relatively insensitive to impact, heat, shock and friction. Additionally, these explosives must possess high power per unit weight, be usable under water, and be of convenient size, shape, and weight for troop use. The following is a brief discussion of military explosives.

8.4.1 Trinitoluene (TNT). See figure 8—17.

8.4.1.1 Description. TNT is the most commonly used military explosive. It is used as a standard to rate other military high explosives. TNT has a detonation velocity of approximately 22,600 fps.

8.4.1.2 Breaching Uses

Charge explosive Booster

8.4.1.3 Construction. ThT is enclosed in an olive drab water resistant fiberboard container that has metal enclosures. One end is provided to receive a blasting cap. The cap well is threaded to receive a priming adapter or the standard coupling base on a firing device.


Size. Military TNT is available ·in 1/4, 1/2, and 1—pound block configurations. Their explosive weight is also calculated using those weights.

RE Factor. 1.00.

Figure 8-17. Demolition Charge 1/4, 1/2, and 1 Pound TNT Blocks

Color. TNT appears bright yellow, brown or gray and turns dark brown with prolonged exposure to sunlight.

Water Resistance. TNT is insoluble in water and can be used in underwater demolitions.

Packaging. TNT is packaged 100 per box for the 1/2 and 1/4 pound blocks and 50 per box for the 1 lb blocks.

DODIC. The DODIC for TNT are:

M041 - 1/4 lb blockM031 - 1/2 lb blockM032 - 1 lb block

8.4.2 Composition C-4. See figure 8-18.

Figure 8—18. M112 Demolition Charge (C—4 Block)

8.4.2.1 Description. Composition C—4 is used for general demolition purposes to include underwater applications. It is particularly effective for cutting steel and timber and for breaching concrete. Detonation velocity is approximately 26,000 fps.


Shape charges Explosively formed penetrators Charge explosive

8.4.2.3 Construction

Explosive. C—4 is a mixture of 91% RDX (cyclotrimethylene trinitramine) and 9% nonexplosive plasticizer. It is a plasticized explosive having the same consistency as putty.

Encasement. C—4 is enclosed in an olive drab plastic bag and sealed with a metal clip. There is a strip of pressure sensitive tape with a paper cover liner protecting the adhesive.


Size. C-4 is a rectangular shaped block, 11 x 2 x 1 inches, weighing 1.25 lb.

RE Factor. 1.34.Color. Odorless and white to light tan in color.

Water Resistance. Excellent in water.

DODIC. The DODIC for Demolition Charge M112 (C-4 block) is:

M023 - Mll2 Demolition Charge.

8.4.3 Sheet Explosive. See figure 8-19.

Figure 8-19. Sheet Explosives

8.4.3.1 Description. Sheet explosive is a versatile, flexible plastic—bonded form of high explosive. Sheet explosive allows the user to quickly apply accurately measured quantities of high explosive in simple and complex patterns. Detonation velocity is approximately 22,000 fps.


Priming systems Charge explosive Kicker charge Explosive continuity (jumpers)

8.4.3.3 Construction. Sheet explosives are composed of a mixture of PETN (pentaerythritol tetranitrate), RDX (cyclotriiaethylene trinitraniirie) or HMX (cyclotetramethylene tetranitrate) and elastomeric binder (various polymers with elastic properties resembling those of natural rubber). The extruded composition has both the appearance and some physical characteristics of rubber.


Size. Sheet explosive weight is expressed in grams per square inch. Sheet explosive is available in a series of thicknesses to provide a range of explosive weight per square inch ofsurface. Thickness for sheet explosive is expressed as C—2, C—3, C—4, etc. The “C” value, 2, 3 and 4, is equal to the grams per square inch. If desired, many thicknesses of explosives may be laminated together to increase the explosive weight for a charge. Refer to table 8—1 for sheet explosive dimensions.

Table 8-1. Sheet Explosive Chart

RE Factor. 1.14.

Color. Sheet explosive is green.

Water Resistance. Sheet explosives are completely waterproof.

Packaging. Sheet explosive is packaged in 20 pound rolls. Each roll is 10 inches wide. The length of each roll is determined by the thickness of the sheet. Sheet explosive is issued by the foot from stock when required.

DODIC. The DODICs for sheet explosives are:

MM27 — Sheet Explosive C-2MM2B - Sheet Explosive C-3MM29 — Sheet Explosive C—4

8.4.4 Booster 20 Gram. See figure 8—20.

Figure 8-20 20 Gram Flexible Charge

8.4.4.1 Description. Booster 20 gram is tubular shaped. Its function is to detonate with high energy in all directions. Boosters have a detonating velocity of approximately 24,000 fps with high brisance. Boosters are compatible with electric, nonelectric, det cord and shock tube firing systems. Boosters are used for highly consistent firing system performance to ensure 100 percent initiation of breaching charges.


Priming systems Charge explosive Kicker charge Explosive continuity (jumpers)

8.4.4.3 Construction. Boosters are composed of a mixture of PETN (pentaerythritol tetranitrate) and elastomeric binder (various polymers with elastic properties resembling those of natural rubber). The extruded composition has both the appearance and some physical characteristics of rubber.


Size. Booster explosive weight is expressed in grams. Boosters are approximately 3 in. long and weigh 20 grams. Boosters have a 0.27 in. hole that runs down the center of the booster that will accept up to 100 gr/ft det cord or blasting cap.

RE Factor. 1.14.

Color. Booster color will vary. Common colors are pink/red, gray, and green.

Water Resistance. Boosters are completely waterproof.

Packaging. Boosters are packaged in a non—standard bulk pack. They are individually issued from stock when required.

DODIC. The DODIC for Booster 20 gram is:

MM3O - Booster 20 gram

8.4.5 Flex Linear Shape Charge (FLSC). See figure 8-21.

8.4.5.1 Description. FLSC is a shaped charge intended to produce a linear cutting action. It cuts through material based on the Monroe effect. The primary advantage is low explosive volume for the work performed. Disadvantages are fragmentation resulting from the covering, jet dispersal, and lead/ copper fumes. Detonating velocity for FLSC is approximately 23,000 to 26,300 fps.

Figure 8-21. Flex Linear Shaped Charge

8.4.5.2 Breaching Use. Charge explosive.

8.4.5.3 Construction. FLSC is shaped in the form of an inverted V.

8.4.5.4 Explosive. FLSC has a continuous explosive core consisting of explosive CH-6 which is 95 percent RDX (cyclotriinethylene trinitrainine) and 5 percent plasticizer.

8.4.5.5 Encasement. FLSC is encased in a lead or copper liner for breaching purposes because its low melting temperature promotes melting and spattering rather than production of sharp, high velocity fragments in the vicinity of the target.


Size. Size is expressed in grains of explosive per foot

(e.g., 40 gr/ft FLSC, 225 gr/ft FLSC, etc.).

RE Factor. 1.35.

Color. Sheathing is shiny to dull gray/ copper.


Packaging. Military FLSC is usually issued in six foot lengths. Lengths of 4 feet may be substituted until depleted from the system.

DODIC. The DODIC5 for the various sizes are:

MM41 - 30 gr/ft FLSC

MM42 - 40 gr/ft FLSCMM43 - 60 gr/ft FLSCMM44 - 75 gr/ft FLSCMM45 - 125 gr/ft FLSCMM46 - 225 gr/ft FLSCMM47 - 400 gr/ft FLSCMM148- 600 gr/ft FLSC

8.4.6 Explosive Cutting Tape (ECT)

8.4.6.1 Description. ECT is also known as Low Hazard Flexible Linear Shaped Charge (LHFLSC), figure 8—22. ECT is a foam jacketed linear shaped charge designed to be non-fragmenting. It may be used in under-water operations to a depth of 32 feet. After 32 feet, the air bubbles in the foam casing compress, reducing the standoff. ECT may be cut with a knife and leaves no residue, toxic fumes and has no fragmentation from the covering. The primary disadvantage is that it takes nearly the double explosive weight of FLSC to do an equal amount of work with ECT. Detonating velocity is in excess of 24,000 fps.

Figure 8-22. Low Hazard Flexible Linear Shaped Charge

8.4.6.2 Breaching Uses. Charge explosive.

8.4.6.3 Construction. ECT is shaped into the form of an inverted “V.

8.4.6.4 Explosive. ECT is a continuous explosive core of SX2 (88 percent cyclonite, 12 percent non-explosive plasticizer).

8.4.6.5 Encasement. ECT is made of two-piece construction, lightweight polyethylene foam. It has a flexible copper-polymer liner. The underside has an adhesive backed tape, which adheres to most dry smooth surfaces.


Size. Size is expressed in grains of explosive per foot

(e.g., 300 gr/ft ECT, 5,400 gr/ft, etc.).

RE Factor. 1.25.

Color. Primarily OD green, but can be other colors. Water Resistance. Excellent.Packaging. ECT is packaged in 20 ft lengths packed in a metal drum. Packaging per drum is as follows:

300 gr/ft 18x20 ft Lengths (360 ft)600 gr/ft 9x20 ft Lengths (180ft)1200 gr/ft 4x20 ft Lengths (80 ft)2400 gr/ft 2x20 ft Lengths (40 ft)5400 gr/ft lx2O ft Lengths (20 ft)

DODIC. The DODICs for the different sizes of ECT are:

~Q~124 300 gr/ftMX 142MOD 0MM51600 gr/ftMX 143MCD 0!~521200 gr/ftMX 144MCD 01fl~532400 gr/ftMX 145MCD 0IQ&545400 gr/ftMX 149MCD 0

8.4.7 Detonating Cord. See figure 8-23.

Figure 8-23. Military Detonating Cord

8.4.7.1 Description. Commonly referred to as det cord, detonating cord is a very strong, flexible cord that contains a core of high explosives. Its function is to deliver an effective detonation wave along its entire length. Depending on the core load, the approximate rate of detonation is between 20,000 and 26,000 fps. This is a rugged explosive ignition system which is less sensitive than most other high explosives to heat, shock, friction, and static electricity.


Priming systems

Charge explosive

8.4.7.3 Construction. Most det cord is two part. The two part det cord consists of an explosive core inside an encasement. Other types of det cord may use multiple strands of two part det cord held together with an outer covering of mesh or plastic. Figure 8-22 shows the construction of military detonating cord (50 grains/foot (gr/ft)).

8.4.7.4 Core High Explosive.

PETN (pentaerythritol tetranitrate) - white powder

RDX (cyclotrimethylene trinitramine) - white powder

8.4.7.5 Encasement. Textile weaves, waterproofing, plastic wire, different colors, and trace threads are used to cover the highly explosive core. Common issue det cord colors include (there may be some variation; do not rely on color to determine size):

Green (50 gr/ ft)White (100 gr/ft)Orange (200 gr/ft)Blue (400 gr/ft)


Size. Det cord size is expressed by the amount of high explosive per foot. The unit of measure is grains per foot (gr/ft). Common issue det cord sizes are as follows:

50 gr/ft (Green) 100 gr/ft (White)200 gr/ft (Orange)400 gr/ft (Blue)

RE Factor. 1.45.

Water Resistance. Det cord ends should be waterproofed with waterproof compound. In addition to sealing the ends, a 6 inch free end will protect the rest of the line from moisture for 24 hours under water.

Packaging. Det cord is issued by the foot. The unit package is either a 500 or 1,000 foot spool.

DODIC. The DODICs for det cord are:

M456 — 50 gr/ft (Green)MU4O — 100 gr/ft (White)MU41 — 200 gr/ft (Orange)MU42 — 400 gr/ft (Blue)

8.5 Diversionary Charges/Devices. A diversion may be defined as anything that distracts the attention. Diversions fall into two broad categories: (1) deceptive, something that deceives, and (2) physiological, something that affects the sensory functions of an organism; e.g., blind or stun momentarily. For the breacher, this may be accomplished with the use of diversionary charges and devices that can be an essential element in an assault plan and should always be incorporated at least as a contingency measure. The use of a diversion must always be rehearsed. These charges and devices may distract or stun a hostile individual long enough to successfully breach a target and accomplish the mission.

8.5.1 Diversionary Charges. These explosive charges are detonated to direct attention away from a mission crisis point. Generally, they are set off prior to or in conjunction with the start of an assault. Diversionary charges are usually bulk explosive charges primed and detonated with a standard initiator. The breacher should use either electric blasting caps or shock tube for detonation. Nonelectric caps and time fuse can be unreliable. Diversionary charges can be enhanced for a particular effect (e.g., bright fireball) with fuel, photoflash powder, or other accelerants.

8.5.2 Diversionary Charge Employment. The keys to successful employment of diversionary charges are coordination, communication, training, and precise planning. Employment requires only that the charge be placed undetected and be detonated at a predetermined time. Some uses include:

Diverting attention away from a crisis point. Initiating an assault. Signaling for a breacher to fire a breaching charge. Causing confusion, disruption, or stunning a hostile force.

8.5.3 MK143. Mod 0 Diversionary Charge. See figure 8-24.

8.5.3.1 Description. This is a small explosive charge in the form of a grenade that produces a disruption or diversion from the main focus of effort. The MX141 Mod 0 diversionary charge is commonly called “flash bangs.”

8.5.3.2 Breaching Use. The MK141 Mod 0 is used to create a diversion.

8.5.3.3 Con struction . The charge is a one piece plastic fuse head extending into a pyrotechnic charge encased in a plastic sleeve and covered with a rigid foam material to minimize the fragmentation hazard. It has a 1.5 second delay and produces 183 dB at 3.5 ft, 11,50a,aOo op peak, and produces shock at 4.2 psi at 3.5 ft.


Size. 5 in. h, 1.75 in. dia.Figure 8-24. MX141 Mod 0 Major Components

Weight. 105 grams.

RE Factor. NA.

Color. Black and white label.

Water Resistance. Water immersion at 26-31 psi, 2 hrs.

Packaging. Sealed in waterproof vacuum-sealed bags, packed 3 per ammo can. The unit of issue is EA.

DODIC. The DODIC for the MK141 Mod 0:

DWBS - Diversionary Charge, MK141 Mod 0

8.5.3.5 Function. Removing the safety pin and releasing the lever will allow the spring loaded striker to initiate the primer and begin a 1.4 second delay which then ignites a separation charge. This results in the fuze/T1 delay assembly separating from the base

a minimum of one foot during the 0.1 second T2 delay before the ignition of the output charge.

8.5.4 Diversionary Device Employment

WARNING

DC NOT RELEASE THE PRESSURE (CALLED “MILKING”) ON THE GRENADEUNTIL ACTUALLY THROWN. THE SAFETY SPOON CAN MOVE PREMATURELY, RELEASING THE FIRING PIN AND CAUSING THE GRENADE TO DETONATE IN THE BREACHER’ S HAND.

Diversionary devices function like most other grenade-type munitions. The safety pin is pulled, the “spoon” releases and separates from the munition body when tossed at a target, the firing pin strikes the primer and after the prescribed delay, the main photoflash filter deteriorates.

The device should be tossed into the center of a target area, as illustrated in figure 8-25. As with charges, use of diversionary devices requires precise planning, coordination, proper training and rehearsal.

Figure 8-25. Employment of MK141 Mod 0 Diversionary Charge

8.5.4.1 Instructions for MK141 MOD 0 Diversionary Charge. Refer to figure 8-26.

Figure 8-26. Safety Pin Angle

WARNING

DO NOT REMOVE THE ADHESIVE ALUMINUM FOIL FROM THE MAIN BODY OF

THE CHARGE. THE FOIL SERVES AS AN ELECTROSTATIC SHIELD.

WARNING

USE OF THE CHARGE CAN CAUSE HEARING DAMAGE. EAR PROTECTION MUST BE WORN THAT WILL PROVIDE THE USER’S EAR PROTECTION FOR 185 dB IMPACT NOISE.

WARNING

THE CHARGE BODY IS MADE OF FOAM. AVOID EXCESSIVE ROUGH HANDLING.

Step 1. Unpackage the charge from the shipping and storage container and remove charge from the barrier bag.

NOTE:Any damaged charge or charge with movement of the fuze relative to the main body shall be disposed of in accordance with local regulations.

Step 2. Immediately inspect the charge for damage. Holding the main body, apply a slight torque to the fuze body. Any charge with movement of the fuze relative to the main body SHALL NOT BE USED.

WARNING

ANY ALTERATION OF THE SAFETY PIN ANGLE (BENDING, FLEXING, REMOVAL AND REINSERTION, CHANGING OF ANGLE, ETC.) FROM THE POSITION OF THE STRAIGHT LEG AND ONE LEG AT 90 DEGREES RELATIVE TO THE OTHER CAN RESULT IN AN INCREASE IN THE PULL FORCE. THIS HIGHER FORCE MAY FRACTURE INTERNAL STRUCTURE THEREBY CAUSING PREMATURE FUNCTION INHANDLING.

Step 3. Remove the red protective sleeve on the straight leg of the safety pin and discard.

Step 4. Prior to pulling safety pin, take action to ensure that one of the safety pin legs is straight and the other leg is bent approximately 90 degrees relative to the other. See figure 8-26, view A.

Step 5. Grasp the charge firmly, holding the safety release lever against the main body and in palm of throwing hand. Hold the fuze body tightly against the main body by curling the index finger and thumb of the throwing hand around the plastic fuze body flange. See figure 8-26, view B.

WARNING

DO NOT REMOVE THE SAFETY PIN UNTIL READY TO USE. ONCE SAFETY PIN HAS

BEEN REMOVED, CHARGE MUST BE THROWN. DO NOT ATTEMPT TO REINSTALL THE SAFETY PIN.

Step 6. Using the other hand, pull on the pull ring to remove the safety pin. See figure 8-26, view C.

Step 7. Do not release the spring loaded safety release lever until thrown.

WARNING

DO NOT LOOK DIRECTLY AT THE DISPLAY OF THE CHARGE.

WARNING

DO NOT ATTEMPT TO RETRIEVE AN ARMED CHARGE.

Step 8. It is recommended that the charge be thrown a minimum distance of ten feet. After the charge has been thrown, turn away.

Step 9. The charge will function between 1.2 and 1.8 seconds after release of spring loaded safety release lever.

NOTE:

The charge is water resistant but is not waterproof. Submersion of the charge in water can cause unsatisfactory performance. The charge should remain in the heat sealed barrier bag until just prior to use.

8.5.5 Non-explosive Materials. These materials help to support the explosive used to make various charges. The materials are available through the Marine Corps supply system. The following describes some of the non-explosive materials used.

Tape. Used for everything from charge construction to charge adhesion to the target. The

types most commonly used are:

Riggers tape, 3/4 and 4 inch.

Mac-Tac/Breachers Tape double—sided tape, all sizes.

Electrical/insulation tape.

Spray Glues. Used for charge construction and adhesion to the target.

Automotive Greases and Breacher Paste. Used for charge adhesion to the target.

Cardboard. Used to make a foundation for the explosives to be supported and to make charges more durable.

Zip Ties. Used to hold charges and Det Cord in place.

Hand Tools. Saws, knives, tape measures, etc., are used to help in the construction of charges. These tools are available in the Pioneer Tool Kits, NSN .

8.6 Net Explosive Weight

8.6.1 General. Different types, amounts, and configurations of explosives will produce different effects on like targets. As discussed in chapter 2, the breacher uses the Breachers Log Book to store information on breaching charges and equipment. A principal element of the Breachers Log Book is the Breaching Report. In order to complete a Breaching Report, breachers must be able to calculate the NEW for charges. NEW calculations are used to determine safe blast and fragmentation distances. Safe blast and fragmentation distances are addressed in chapter 9. A breacher’s ability to accurately determine the NEW for explosive charges will allow operational training to be conducted at the highest level of realism possible to meet mission readiness requirements. This training gives the assault force the ability to safely stack close to the breach point without sacrificing speed, surprise, and violence of action.

8.6.2 Unit of Measure. The NEW for explosive charges is expressed in pounds TNT equivalent. This is the simplest approach to explain in briefings and is the unit of measure and type of explosive that personnel are the most familiar with. All NEW calculations will be figured out to thousandths (three places) of a pound and rounded off to hundredths (two places) of a pound. To round of f a decimal:

(1) If first digit to right of round-off place is less than 5: digit in round off place is unchanged.

3.244 = 3.24

If first digit to right of round-off place is 5 or more:

digit in round off place is increased by 1.

3.247 = 3.25

(2) Digits to left of round off place are unchanged.

3.244 or 3.247 = 3.24 or 3.25

(3) Digits to right of both round off place and decimal point are dropped.

3.24333 or 3.24722 = 3.24 or 3.25

Digits to right of round off place and left of decimal point are replaced by zeros.

0.999 or .899 = 1.00 or 0.90

8.6.3 The Formula . The formula for calculating NEW for explosive charges is:

NEW = W (in TNT equivalent)7000

(1) NEW is the net explosive weight in pounds of a given explosive charge equivalent to the weight in TNT.

(2) W is the weight of all explosives, including blasting caps in grains used to construct the charge and priming system converted to TNT equivalent.

(3) 7000 is the conversion factor for converting grains to pounds.

8.6.4 Use of the Formula. Use the formula in the following manner:

All explosives, including blasting caps, used to construct the charge and priming system will be included in NEW calculations.

(1) Determine the total amount of explosive involved by weight. Explosive weights and measures can be found in this chapter under the characteristics heading of each explosive that is discussed.

(2) Ensure that the total weight is expressed in grains. If not, use the appropriate conversion table in appendix F and multiply the weight of the type of explosive used by the conversion factor to determine the grains.

(3) Multiply weight in grams by the RE factor for that explosive to get grams TNT equivalent. Refer to the appropriate table in chapter 9.

(4) Add the weight equivalent in TNT of all components together.

(5) Divide the weight of all components equivalent in TNT by 7000.

Calculations for NEW should be figured out to thousandths (three places) of a pound and rounded off to hundredths (two places) of a pound.

(6) The weight provided is in pounds TNT equivalent and can be used to determine the stack point, anticipated overpressure, and fragmentation hazards.

8.6.5 Sample Calculations. See tables 8—2, 8—3, and 8—4.

(1) You have 25 feet of 50 gr/ft detonating cord and 6 feet of 400 gr/ft detonating cord.

Table 8-2. Example 1 for Determining TNT Equivalent

(2) You have 12 feet of 40 gr/ft FLSC, 1 booster 20 gram, 3 feet of 50 gr/ft detonating cord, and a 3” x 5” piece of C-3 sheet explosive.


(3) You have 1.25 pounds of C-4 explosive, 12 inches of 50 gr/ft detonating cord, and 2 blasting caps.


ARMY - Chapter Eight Explosive Breaching

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