Improvised Munitions Handbook (Improvised Explosive Devices or IEDs)

# Section 6
Fuses, Detonators & Delay Mechanisms

## 6.1 Electric Bulb Initiator

Mortars, mines and similar weapons often make use of electric initiators. An electric initiator can be made using a flash light or automobile electric light bulb.

Materials Required
Electric light bulb and mating socket
Cardboard or heavy paper
Black powder
Adhesive tape

#### Procedure

##### Method I

1. Break the glass of the electric light bulb. Take care not to damage the filament. The initiator will not work if the filament is broken. Remove all glass above the base of the bulb.

2. Form a tube 3 to 4 inches long from cardboard or heavy paper to fit around the base of the bulb. Join the tube with adhesive tape.

3. Fit the tube to the bulb base and tape in place.

Make sure that the tube does not cover that portion of the bulb base that fits into the socket.

4. If no socket is available for connecting the initiator to the firing circuit, solder the connecting wires to the bulb base.

Caution: Do not use a hot soldering iron on the completed igniter since it may ignite the black powder.

5. Fill the tube with black powder and tape the open end of the tube closed.

##### Method II

If the glass bulb (electric light) is large enough to hold the black powder, it can be used as the container.

#### Procedure

1. File a small hole in the top of the bulb.

2. Fill the bulb with black powder and tape the hole closed.

## 6.2 Fuse Igniter from Book Matches

A simple, reliable fuse igniter can be made from paper book matches.

Materials Required
Paper book matches
Adhesive or friction tape
Fuse cord (improvised or commercial)
Pin or small nail

#### Procedure

1. Remove the staple(s) from match book and separate matches from cover.

2. Cut fuse cord so that inner core is exposed.

3. Tape exposed end of fuse cord in center of one row of matches.

4. Fold matches over fuse and tape.

5. Shape the cover into a tube with the striking surface on the inside and tape. Make sure the edges of the cover at the striking end are butted. Leave cover open at opposite end for insertion of the matches.

6. Push the taped matches with fuse cord into the tube until the bottom ends of the matches are exposed about 3/4 inch (2 cm).

7. Flatten and fold the open end of the tube so that it laps over about 1 inch (2-1/2 cm); tape in place.

8. Push pin or small nail through matches and fuse cord. Bend end of pin or nail.

#### Method of Use

To light the fuse cord, the igniter is held by both hands and pulled sharply or quickly.

Caution: Store matches and completed fuse igniters in moistureproof containers such as plastic or rubber type bags until ready for use. Damp or wet paper book matches will not ignite. Fuse lengths should not exceed 12 inches (30 cm) for easy storage. These can be spliced to main fuses when needed.

## 6.3 Delay Igniter from Cigarette

A simple and economical time delay can be made with a common cigarette.

Materials Required
Cigarette
Paper match
String (shoelace or similar cord)
Fuse cord (improvised or commercial)

#### Procedure

1. Cut end of fuse cord to expose inner core.

2. Light cigarette in normal fashion. Place a paper match so that the head is over exposed end of fuse cord and tie both to the side of the burning cigarette with string.

3. Position the burning cigarette with fuse so that it burns freely. A suggested method is to hang the delay on a twig.

Note:

Common dry cigarettes burn about 1 inch every 7 or 8 minutes in still air. If the fuse cord is placed 1 inch from the burning end of a cigarette a time delay of 7 or 8 minutes will result.

Delay time will vary depending upon type of cigarette, wind, moisture, and other atmospheric conditions.

To obtain accurate delay time, a test run should be made under “use” conditions.

## 6.4 Watch Delay Timer

A time delay device for use with electrical firing circuits can be made by using a watch with a plastic crystal.

Materials Required
Watch with plastic crystal
Small clean metal screw
Battery
Connecting wires
Drill or nail

#### Procedure

1. If watch has a sweep or large second hand, remove it. If delay time of more than one hour is required, also remove the minute hand. If hands are painted, carefully scrape paint from contact edge with knife.

2. Drill a hole through the crystal of the watch or pierce the crystal with a heated nail. The hole must be small enough that the screw can be tightly threaded into it.

3. Place the screw in the hole and turn down as far as possible without making contact with the face of the watch. If screw has a pointed tip, it may be necessary to grind the tip flat.

If no screw is available, pass bent stiff wire through the hole and tape to the crystal.

Important: Check to make sure hand of watch cannot pass screw or wire without contacting it.

#### How to Use

1. Set the watch so that a hand will reach the screw or wire at the time you want the firing circuit completed.

2. Wind the watch.

3. Attach a wire from the case of the watch to one terminal of the battery.

4. Attach one wire from an electric initiator (blasting cap, squib, or alarm device) to the screw or wire on the face of the watch.

5. After thorough inspection is made to assure that the screw or the wire connected to it is not touching the face or case of the watch, attach the other wire from the initiator to the second terminal of the battery.

Caution: Follow step 5 carefully to prevent premature initiation.

## 6.5 No-Flash Fuse Igniter

A simple no-flash fuse igniter can be made from common pipe fittings.

Materials Required
1/4 inch (6 mm) pipe cap
Solid 1/4 inch (6 mm) pipe plug
Flat head nail about 1/16 inch (1-1/2 mm) in diameter
Hand drill
Common “strike-anywhere” matches
Adhesive tape

#### Procedure

1. Screw the pipe plug tightly into the pipe cap.

2. Drill hole completely through the center of the plug and cap large enough that the nail fits loosely.

3. Enlarge the hole in the plug except for the last 1/8 inch (3 mm) so that the fuse cord will just fit.

4. Remove the plug from the cap and push the flat head nail through the hole in the cap from the inside.

5. Cut the striking tips from approximately 10 “strike-anywhere” matches. Place match tips inside pipe cap and screw plug in finger tight.

#### How to Use

1. Slide the fuse cord into the hole in the pipe plug.

2. Tape igniter to fuse cord.

3. Tap point of nail on a hard surface to ignite the fuse.

## 6.6 Dried Seed Timer

A time delay device for electrical firing circuits can be made using the principle of expansion of dried seeds.

Materials Required
Dried peas, beans or other dehydrated seeds
Wide mouth glass jar with nonmetal cap
Two screws or bolts
Thin metal plate
Hand drill
Screwdriver

#### Procedure

1. Determine the rate of rise of the dried seeds selected. This is necessary to determine delay time of the timer.

1. Place a sample of the dried seeds in the jar and cover with water.
2. Measure the time it takes for the seeds to rise a given height. Most dried seeds increase 50% in one to two hours.

2. Cut a disc from thin metal plate. Disc should fit loosely inside the jar.

Note: If metal is painted, rusty or otherwise coated, it must be scraped or sanded to obtain a clean metal surface.

3. Drill two holes in the cap of the jar about 2 inches apart. Diameter of holes should be such that screws or bolts will thread tightly into them. If the jar has a metal cap or no cap, a piece of wood or plastic (not metal) can be used as a cover.

4. Turn the two screws or bolts through the holes in the cap. Bolts should extend about one inch (2-1/2 cm) into the jar.

Important: Both bolts must extend the same distance below the container cover.

5. Pour dried seeds into the container. The level will depend upon the previously measured rise time and the desired delay.

6. Place the metal disc in the jar on top of the seeds.

#### How to Use

1. Add just enough water to completely cover the seeds and place the cap on the jar.

2. Attach connecting wires from the firing circuit to the two screws on the cap.

Expansion of the seeds will raise the metal disc until it contacts the screws and closes the circuit.

## 6.7 Fuse Cords

These fuse cords are used for igniting propellants and incendiaries or, with a nonelectric blasting cap, to detonate explosives.

### 6.7.1 Fuse Cords — Fast Burning Fuse

The burning rate of this fuse is approximately 40 inches (100 cm) per minute.

Materials Required
Soft cotton string
Fine black powder | or |
Potassium nitrate (saltpeter) | 25 parts
Charcoal | 3 parts
Sulfur | 2 parts
Piece of round stick
Two pans or dishes

#### Procedure

1. Moisten fine black powder to form a paste or prepare a substitute as follows:

1. Dissolve potassium nitrate in an equal amount of water.
2. Pulverize charcoal by spreading thinly on a hard surface and rolling the round stick over it to crush to a fine powder.
3. Pulverize sulfur in the same manner.
4. Dry mix sulfur and charcoal.
5. Add potassium nitrate solution to the dry mix to obtain a thoroughly wet paste.

2. Twist or braid three strands of cotton string together.

3. Rub paste mixture into twisted string with fingers and allow to dry.

4. Check actual burning rate of fuse by measuring the time it takes for a known length to burn. This is used to determine the length needed for a desired delay time. If 5 inches (12-1/2 cm) burns for 6 seconds, 50 inches (125 cm) of fuse cord will be needed to obtain a one minute (60 second) delay time.

### 6.7.2 Fuse Cords — Slow Burning Fuse

The burning rate of this fuse in approximately 2 inches (5 cm) per minute.

Materials Required
Cotton string or 3 shoelaces
Potassium nitrate or potassium chlorate
Granulated sugar

#### Procedure

1. Wash cotton string or shoelaces in hot soapy water; rinse in fresh water.

2. Dissolve 1 part potassium nitrate or potassium chlorate and 1 part granulated sugar in 2 parts hot water.

3. Soak string or shoelaces in solution.

4. Twist or braid three strands of string together and allow to dry.

5. Check actual burning rate of the fuse by measuring the time it takes for a known length to burn. This is used to determine the length needed for the desired delay time. If 2 inches (5 cm) burns for 1 minute, 10 inches (25 cm) will be needed to obtain a 5 minute delay.

Note: The last few inches of this cord (the end inserted in the material to be ignited) should be coated with the fast burning black powder paste if possible. This must be done when the fuse is used to ignite a blasting cap.

Remember: The burning rate of either of these fuses can vary greatly. Do not use for ignition until you have checked their burning rate.

## 6.8 Clothespin Time Delay Switch

A 3 to 5 minute time delay switch can be made from the clothespin switch (section 7.1) and a cigarette. The system can be used for initiation of explosive charges, mines, and booby traps.

Materials Required
Spring type clothespin
Solid or stranded copper wire about 1/16 inch (2 mm) in diameter (field or bell wire is suitable)
Fine string, about 6 inches in length
Cigarette
Knife

#### Procedure

1. Strip about 4 inches (10 cm) of insulation from the ends of 2 copper wires. Scrape copper wires with pocket knife until metal is shiny.

2. Wind one scraped wire tightly on one jaw of the clothespin, and the other wire on the other jaw so that the wires will be in contact with each other when the jaws are closed.

3. Measuring from tip of cigarette measure a length of cigarette that will correspond to the desired delay time. Make a hole in cigarette at this point, using wire or pin.

Note: Delay time may be adjusted by varying the burning length of the cigarette. Burning rate in still air is approximately 7 minutes per inch (2.5 cm). Since this rate varies with environment and brand of cigarette, it should be tested in each case if accurate delay time is desired.

4. Thread string through hole in cigarette.

5. Tie string around rear of clothespin, 1/8 inch or less from end. The clothespin may be notched to hold the string in place.

Note: The string must keep the rear end of the clothespin closed so that the jaws stay open and no contact is made between the wire.

#### How to Use

Suspend the entire system vertically with the cigarette tip down. Light tip of cigarette. Switch will close and initiation will occur when the cigarette burns up to and through the string.

Note: Wires to the firing circuit must not be pulled taut when the switch is mounted. This could prevent the jaws from closing.

## 6.9 Time Delay Grenade

This delay mechanism makes it possible to use an ordinary grenade as a time bomb.

Materials Required
Grenade
Fuse cord

Important: Fuse cord must be the type that burns completely. Slow burning improvised fuse cord (section 6.7) is suitable. Safety fuse is not satisfactory, since its outer covering does not burn.

#### Procedure

1. Bend end of safety lever upward to form a hook. Make a single loop of fuse cord around the center of the grenade body and safety lever. Tie a knot of the nonslip variety at the safety lever.

Note: The loop must be tight enough to hold the safety lever in position when the pin is removed.

2. Measuring from the knot along the free length of the fuse cord, measure off a length of fuse cord that will give the desired delay time. Cut off the excess fuse cord.

#### How to Use

1. Place hand around grenade and safety lever so safety lever is held in place. Carefully remove pin.

2. Emplace grenade in desired location while holding grenade and safety lever.

3. Very carefully remove hand from grenade and safety lever, making sure that the fuse cord holds the safety lever in place.

Caution: If loop and knot of fuse cord do not hold for any reason and the safety lever is released, the grenade will explode after the regular delay time.

4. Light free end of fuse cord.

## 6.10 Can-Liquid Time Delay

A time delay device for electrical firing circuits can be made using a can and liquid.

Materials Required
Can
Liquid (water, gasoline, etc.)
Small block of wood or any material that will float on the liquid used
Knife
2 pieces of solid wire, each piece 1 foot (30 cm) or longer

#### Procedure

1. Make 2 small holes at opposite sides of the can very close to the top.

2. Remove insulation from a long piece of wire for a distance a little greater than the diameter of the can.

3. Secure the wire in place across the top of the can by threading it through the holes and twisting in place, leaving some slack. Make loop in center or wire. Be sure a long piece of wire extends from one end of the can.

4. Wrap a piece of insulated wire around the block of wood. Scrape insulation from a small section of this wire and bend as shown so that wire contacts loop before wood touches bottom of container. Thread this wire through the loop of bare wire.

5. Make a very small hole (pinhole) in the side of the container. Fill container with a quantity of liquid corresponding to the desired delay time. Since the rate at which liquid leaves the can depends upon weather conditions, liquid used, size of hole, amount of liquid in the container, etc., determine the delay time for each individual case. Delays from a few minutes to many hours are possible. Vary time by adjusting liquid level, type of liquid (water, oil) and hole size.

#### How to Use

1. Fill can with liquid to the same level as during experimental run (step 5 above). Be sure that wooden block floats on liquid and that wire is free to move down as liquid leaves container.

2. Connect wires to firing circuit.

Note: A long term delay can be obtained by placing a volatile liquid (gasoline, ether, etc.) in the can instead of water and relying on evaporation to lower the level. Be sure that the wood will float on the liquid used. Do not make pinhole in side of can!

## 6.11 Short Term Time Delay for Grenade

A simple modification can produce delays of approximately 12 seconds for grenades when fired from Grenade Launchers (section 4.5).

Materials Required
Grenade |
Nail
Knife | May not be needed
Pliers
Safety fuse |

Note: Any safety or improvised fuse may be used. However, since different time delays will result, determine the burning rate of the fuse first.

#### Procedure

1. Unscrew fuse mechanism from body of grenade and remove. Pliers may have to be used.

2. Carefully cut with knife or break off detonator at crimp and save for later use.

Caution: If detonator is cut or broken below the crimp, detonation may occur and severe injuries could result.

3. Remove safety pin pull ring and lever, letting striker hit the primer. Place fuse mechanism aside until delay fuse powder mix in mechanism is completely burned.

4. Remove pin, spring, and striker.

5. Remove primer from fuse mechanism by pushing nail through bottom end of primer hole and tapping with hammer.

6. Insert safety fuse through top of primer hole. Enlarge hole if necessary. The fuse should go completely through the hole.

7. Insert fuse into detonator and tape it securely to modified fuse mechanism.

Note: Be sure that fuse rests firmly against detonator at all times.

8. Screw modified fuse mechanism back into grenade. Grenade is now ready for use.

Note: If time delay is used for Improvised Grenade Launchers (section 4.5):

1. Wrap tape around safety fuse.

2. Securely tape fuse to grenade.

3. Load grenade in launcher. Grenade will explode in approximately 12 seconds after safety fuse burns up to bottom of grenade.

## 6.12 Long Term Time Delay for Grenade

A simple modification can produce delays of approximately 20 seconds for grenades when fired from Grenade Launchers (section 4.5).

Materials Required
Grenade
Nail
“Strike-anywhere” matches, 6 to 8
Pliers (may not be needed)
Knife or sharp cutting edge
Piece of wood
Safety fuse

Note: Any safety or improvised fuse may be used. However, since different time delays will result, determine the burning rate of the fuse first.

#### Procedure

1. Unscrew fuse mechanism from body of grenade and remove. Pliers may have to be used.

2. Insert nail completely through safety hole (hole over primer).

3. Carefully remove safety pin pull ring and lever, and allow striker to hit nail.

Caution: If for any reason, striker should hit primer instead of nail, detonator will explode after (4–5 second) delay time.

4. Push pin out and remove spring and striker. Remove nail.

5. Carefully remove top section of fuse mechanism from bottom section by unscrewing. Pliers may have to be used.

Caution: Use extreme care—sudden shock may set off detonator.

6. Fire primer by hitting nail placed against top of it. Remove fired primer (same as step 5 of section 6.11).

Caution: Do not hold assembly in your hand during above operation, as serious burns may result.

7. Scrape delay fuse powder with a sharpened stick. Loosen about 1/4 inch (6 mm) of powder in cavity.

8. Cut off tips (not whole head) of 6 "strike-anywhere" matches with sharp cutting edge. Drop them into delay fuse hole.

9. Place safety fuse in delay fuse hole so that it is flush against the match tips.

Important: Be sure fuse remains flush against the match tips at all times.

10. Thread fuse through primer hole. Enlarge hole if necessary. Screw modified fuse mechanism back together. Screw combination back into grenade. Grenade modification is now ready for use. Light fuse when ready to use.

Note: If time delay is used for Improvised Grenade Launchers (section 4.5):

1. Wrap tape around safety fuse.

2. Securely tape fuse to grenade.

3. Load grenade in launcher. Grenade will explode in approximately 20 seconds after safety fuse burns up to bottom of grenade.

## 6.13 Detonator

Detonators (blasting caps) can be made from a used small arms cartridge case and field manufactured explosives. Detonators are used to initiate secondary high explosives (C4, TNT, etc.).

Materials Required | Source
--- | ---
Primary explosive | See table
Booster explosive | RDX (section 1.15) or picric acid (section 1.21)
Improvised scale | Section 7.8
Used cartridge case | .22 caliber or larger
Fuse, 12 inches long |
Round wooden stick (small enough just to fit in the neck of the cartridge case) |
Drill or knife |
Long nail with sharpened end |
Vise |
Improvised loading fixture |

#### Procedure

1. Remove fired primer from a used cartridge case using a sharpened nail. (See section 3.5.)

2. If necessary, open out flash hole in the primer pocket using a drill or knife. Make it large enough to receive fuse.

3. Place one end of fuse in the flash hole and extend it through the case until it becomes exposed at the open end. Knot this end and then pull fuse in cartridge case thus preventing fuse from falling out.

4. Load the primary explosive in the cartridge case, using the following table for the proper amount.

Primary Explosive | Primary Explosive Source | Minimum Weight*
--- | --- | ---
Lead picrate** | Section 1.20 | 3 grams (3 handbook pages)
TACC (tetramminecopper chlorate) | Section 1.16 | 1 gram (1 handbook page)
DDNP (diazodinitrophenol) | Section 1.19 | 0.5 gram (1/2 handbook page)
Mercury fulminate | Section 1.24 | 0.75 gram (3/4 handbook page)
HMTD | Section 1.17
Double salts | Section 1.22

*See section 7.8 for details on improvised scale.
**.22 caliber cartridge case cannot be used with lead picrate as there is not enough volume to contain the explosive train.

5. Compress the primary explosive into the cartridge case with the wooden stick and the following improvised loading fixture.

Caution: The primary explosive is shock and flame sensitive.

Note: Tamping is not needed when TACC is used.

6. Add one gram of booster explosive. The booster can be RDX (section 1.15), or picric acid (section 1.21).

7. Compress the booster explosive into the cartridge case with wooden stick and the loading fixture.

8. If the case is not full, fill the remainder with the secondary explosive to be detonated.

Caution: Detonator has considerably more power than a military blasting cap and should be handled carefully.