Pipe bomb

For the professional wrestling term, see Shoot (professional wrestling). For the website, see Thepipebomb.com.

A tripwire-triggered pipe bomb mock-up, used to train U.S. military service personnel.

A pipe bomb is an hand-throwable anti-personnel improvised explosive device (IED), ^[1] a bomb made from a piece of pipe. ^[2]

From a technical point of view, a pipe bomb is a mechanically strong containment device, filled with an explosive material, that allows pressure to build until it exceeds the strength of the container at its weakest point; the device is designed to rupture and not to fail at a specific joint, thus resulting in a catastrophic destruction of the container, usually followed by the ejection of sharp shrapnels moving at high speed in all directions. ^[3]

It has been used primarily by violent non-state actors ^[1] in guerrilla warfare or in terrorist operations. More rarely, it has been used by the regular armed forces of some countries.

In many countries, the manufacture or possession of a pipe bomb is a serious crime, regardless of its intended use.

Design

Several examples of pipe bombs. The top one has its ends closed by crimpings; the bottom one has intersecting grooves.

The construction characteristics of a pipe bomb – like the characteristics of any improvised explosive device – are determined by the materials, technical knowledge, and inventiveness available to its manufacturer. These factors make it impossible to exhaustively list all the possible variants of this device. However, it is possible to highlight three elements that are specific to all pipe bombs: an explosive charge, a pipe, and an initiator. ^{[5] [6]}

Usually the explosive charge consists of a low explosive of low or medium power: smokeless powder obtained from small arms cartridges (pistols or rifles); ^[7] black powder; ^{[1] [8]} flash powder obtained from fireworks; ^{[1] [8]} safety match heads; ^{[8] [9]} cheddites (i.e. explosives composed primarily of chlorates or perchlorates of potassium, sodium or ammonium); ^{[1] [10]} etc. More rarely, the explosive charge can consist of a high explosive, such as dynamite. ^{[6] [11]}

The pipe containing the explosive charge is usually a common galvanized metal pipe, such as an iron or steel plumbing pipe. The manufacturer may have made intersecting grooves on the outer surface and/or attached nails, nuts, bolts, ball bearings, etc., to increase the number of shrapnel and fragments projected. A pipe bomb constructed in this way can be roughly compared to a factory-made defensive fragmentation grenade. The pipe can also be made of lightweight sheet metal or plastic (PVC). With this configuration, the pipe bomb can be roughly compared to an offensive blast grenade, which damages the target not through shrapnel but through the local overpressure generated by the explosive charge. In both cases, the pipe is closed at both ends with threaded caps or by crimpings. A small hole is made on the surface of the pipe or on one of the caps, in order to pass the initiator through. ^{[5] [6]}

Diagram of a pipe bomb equipped with a fuse connected to a detonator.

The initiator can vary depending on the nature of the explosive charge: if the pipe bomb contains a low explosive such as black powder, the initiator can be a simple fuse; if, instead, it contains an high explosive such as dynamite, etc. then the fuse is connected to a detonator. The initiator can also vary depending on the "mission" that the manufacturer intends the pipe bomb to perform: for example, if he wants to detonate it at a specific time, it is possible that he connects the detonator to an electrical circuit including cables, batteries, timers, switches, etc. ^{[5] [6]}

Pipe bomb construction, besides being illegal in most jurisdictions and under most laws around the world, is also a dangerous activity. ^{[12] [5]} Many pipe bomb builders have been injured, maimed, or killed by their own device due to accidental sparks (created by the explosive substance friction against the threads or uninsulated internal walls of the metal pipe), ^{[13] [5]} electrostatic discharges, ^[13] chemically unstable improvised detonators, etc. These risks can be further increased if the builder adds pieces of metal to the inside of the pipe.

Operation

Pipe bombs concentrate pressure and release it suddenly, through the failure of the outer casing. Plastic materials can be used, but metals typically have a much higher bursting strength and so will produce more concussive force. For example, common schedule 40 1-inch (25 mm) wrought steel pipe has a typical working pressure of 1,010 psi (7.0 MPa), and bursting pressure of 8,090 psi (55.8 MPa), ^[14] though the pipe sealing method can significantly reduce the burst pressure.

The pipe can rupture in different ways, depending on the rate of pressure rise and the ductility of the casing material.

• If the pressure rise is slow, the metal can deform until the walls become thin and a hole is formed, causing a loud report from the gas release, but no shrapnel.
• A rapid rate of pressure rise will cause the metal to shatter into fragments, which are pushed outward in all directions by the expanding gases.

Modes of failure

Serious injuries caused by the premature explosion of a pipe bomb.

Premature detonation is a hazard of attempting to construct any homemade bomb. The materials and methods used with pipe bombs often result in unintentional detonation, usually resulting in serious injury or death to the assembler.

Pipe bombs can fail to explode if the gas pressure buildup is too slow, resulting in bleed-out through the detonator ignition hole. Insufficiently tight threading can also bleed gas pressure through the threads faster than the chemical reaction pressure can rise.

They can also fail if the pipe is fully sealed and the chemical reaction triggered, but the total pressure buildup from the chemicals is insufficient to exceed the casing strength; such a bomb inevitably fails to trigger, but is still potentially dangerous if handled, since an external shock could trigger rupture of the statically pressurized casing.

Minimum evacuation distances

If any type of bomb is suspected, typical recommendations are to keep all people at a minimum evacuation distance until authorized bomb disposal personnel arrive. For a pipe bomb, the U.S. Department of Homeland Security recommends a minimum of 21 m (70 ft), and an outdoors distance of 259 m (850 ft). ^[15]

Uses

Pipe bombs were adopted and used successfully by some regular armed forces, for example during World War I (1914–1918), the Spanish Civil War (1936–1939) ^[16] and World War II (1939–1945). During the First World War, among the hand grenades supplied to the Italian infantry, there was a pipe bomb called "hand-held piece" (Italian : spezzone a mano); ^[17] during the Second World War, training for the Home Guard, the auxiliary force of the British Army, also included the production and use of pipe bombs. ^[16]

Pipe bombs are by nature improvised weapons and typically used by those without access to military devices such as grenades.

In Northern Ireland, there have been hundreds of pipe bomb attacks since the mid-1990s as the Troubles came to an end. Most of the attacks have been launched by loyalist paramilitaries, especially the Red Hand Defenders, Orange Volunteers and Ulster Defence Association. ^{[18] [19]} However, they have also been used by Irish republican paramilitaries and by anti-drugs vigilante group Republican Action Against Drugs. They are also used extensively in the south of Ireland by feuding criminals, including drug dealers, mainly in the capital city of Dublin.

As well as users such as criminals, paramilitaries, and militias, they also have a long tradition of recreational use for amusement or mischief with no intention to cause injury to anyone, but due to the dangers of premature ignition and of shrapnel, pipe bombs are much more dangerous than alternatives, such as dry ice bombs or potato cannons.

Notable incidents

This 1886 engraving was the most widely reproduced image of the Haymarket riots. It inaccurately shows Fielden speaking, the pipe bomb exploding, and the rioting beginning simultaneously.

• On 4 May 1886, a pipe bomb was thrown during a rally at Haymarket Square in Chicago, Illinois, United States. ^[11] It reached a police line and exploded, killing policeman Mathias J. Degan. ^[11] The bomb was made from gas-pipe filled with dynamite and capped at both ends with wooden blocks. ^[11]
• From August 1977 to November 1977 Allan Steen Kristensen planted several bombs across Copenhagen, Denmark injuring 5.
• In 1985, Palestinian American anti-discrimination activist Alex Odeh was killed in California by a pipe-bomb. Activists from the Jewish Defense League are suspected of being the bombers. ^{[21] [22]}
• On 16 December 1989, Federal Judge Robert Vance was assassinated in his home in Mountain Brook, Alabama when he opened a package that contained a pipe bomb mailed by Walter Leroy Moody in Mountain Brook, Alabama.^{[ citation needed ]}
• On 27 July 1996, Eric Rudolph used a pipe bomb in the Centennial Olympic Park bombing during the 1996 Summer Olympics in Atlanta, Georgia, United States. It killed two people and injured 111. ^[23]
• During the preparation of the Columbine High School massacre, Eric Harris and Dylan Klebold had experimented with pipe bombs. During their testing and experimentation, Eric Harris had posted their results on his website. During the massacre, Harris and Klebold had used their pipe bombs as makeshift hand grenades, alongside various other bombs they had crudely manufactured.
• On 11 December 2010 a suicide bomber detonated one out of six pipe bombs close to a major shopping district in Stockholm, Sweden, killing himself with no other casualties in what is known as the 2010 Stockholm bombings. ^[24]
• In October 2018, pipe bombs without triggering devices ^[25] were sent to various liberal and political figures in the United States. Recipients included political activist and investor George Soros, former secretary of state Hillary Clinton, former President Barack Obama, former CIA director John Brennan, and former attorney general Eric Holder. ^{[26] [27]}
• On 6 January 2021, a pipe bomb was found at the headquarters of the Republican National Committee, during the certification of President-elect Joe Biden. An unidentified object was also found at the headquarters of the Democratic National Committee, resulting in an evacuation. These findings are likely connected to the riot that day. ^[28] A suspect was arrested in December 2025. ^[29]

See also

• Improvised explosive device
• Jam tin grenade
• Nail bomb
• TM 31-210 Improvised Munitions Handbook

References

1. "Chapter 11: Irregular Forces". Worldwide Equipment Guide. Vol. 1: Ground Systems. Fort Leavenworth, KS: U.S. Department of the Army. December 2015. p.  23.
2. "Definition of PIPE BOMB". merriam-webster.com. Archived from the original on 29 December 2025.
3. Bell, Suzanne (2013). Forensic chemistry (2 ed.). Boston: Pearson. pp.  365, 367. ISBN   978-0321765758.
4. "Overseas Bomb Threat Awareness" (PDF). 2009-2017.state.gov. U.S. Department of State - Bureau of Diplomatic Security. p. 4. Archived from the original (PDF) on 23 July 2025.
5. Scott, Lee (1994). Pipe and Fire Bomb Designs: A Guide for Police Bomb Technicians. Boulder, CO, USA: Paladin Press. ISBN   0-87364-780-7.
6. Smith, Jim (2003). A Law Enforcement and Security Officers' Guide to Responding to Bomb Threats : Providing Working Knowledge of Bombs, Preparing for Such Incidents, and Performing Basic Analysis of Potential Threats. Springfield, IL: Charles C Thomas Publisher. pp. 48–52. ISBN   0-398-07374-0. LCCN   2002073241.
7. Headquarters, Department of the Army (1969). TM 31-210 Improvised Munitions Handbook (PDF). Washington D.C.: United States Department of War. p. 73. Archived from the original (PDF) on 9 July 2025.
8. "Virginia Department of Forensic Science - Evidence Handling & Laboratory Capabilities Guide - Trace Evidence: Explosives" (PDF). dfs.virginia.gov. Virginia Department of Forensic Science. p. 2. Archived from the original (PDF) on 10 September 2023.
9. ST 31-180 Special Forces Handbook (PDF). U.S. Army J.F.K. Special Warfare Center. January 1965. p. III-25 – III-26.
10. J. Horrocks, Aaron; Detata, David; Pitts, Kari; W. Lewis, Simon. "Chlorate-based homemade explosives: A review". Wires Forensic Science. 6 (2). doi: 10.1002/wfs2.1506 . ISSN   2573-9468. Archived from the original on 26 February 2024.
11. Lawson, John Davison; Robert Lorenzo Howard (1919). American State Trials: A Collection of the Important and Interesting Criminal Trials which Have Taken Place in the United States from the Beginning of Our Government to the Present Day. Thomas Law Books. p.  64. A gas-pipe was to be taken and a wooden plug put into the ends, and it was to be filled with dynamite. Then the other end is also closed up with a wooden plug and old nails are tied around the pipe by means of wire. Then a hole is bored into one end of it, and a fuse with a cap is put into that hole.
12. Dias, Gary A.; Dingeman, Robbie (2004). Honolulu CSI: An Introduction to Forensic Science and Criminal Investigation. Honolulu, HI, USA: Bess Press. p.  87. ISBN   978-1-57306-228-2.
13. Thurman, James T. (2017). Practical Bomb Scene Investigation (3 ed.). Boca Raton - London - New York: CRC Press - Taylor & Francis Group. pp. 12–13. ISBN   978-1-4987-7308-9.
14. Wrought Steel Pipe - Bursting Pressures. "The bursting pressures are based on Barlow's formula. The working pressures are based on factor 8. Dimensions according ASME/ANSI B36.10/19". www.engineeringtoolbox.com.
15. "Bomb Threat Stand-Off Distances" (PDF). The National Counterterrorism Center. Archived (PDF) from the original on 26 April 2017.
16. McCutcheon, Campbell, ed. (2006) [1941]. Home Guard Manual 1941. London: Tempus Publishing Limited. p.  74. ISBN   0-7524-3887-5.
17. R. Esercito Italiano, Comando Supremo, Ufficio Affari Vari, Sezione Istruzioni (1917). Istruzione sulle Bombe a Mano e da Fucile [Hand and Rifle Grenades Training](PDF) (in Italian). Roma: Lab. Tip. del Comando del Corpo di Stato Maggiore. p. 14. Archived from the original (PDF) on 18 January 2024.
18. Wood, Ian.S (2006). Crimes of Loyalty: A History of the UDA. p. 248. ISBN   978-0-7486-2427-0.
19. Gassman, Michele. "Violence - Chronology of 'Pipe-Bomb' Attacks". Conflict Archive on the Internet . Retrieved 5 January 2021.
20. "Act II: Let Your Tragedy Be Enacted Here, Moment of Truth". The Dramas of Haymarket. Chicago Historical Society. 2000. Archived from the original on 15 March 2008. Retrieved 19 January 2008. The details are factually incorrect, because by all accounts Fielden ended his speech before the bomb was thrown, and because the riot did not begin until after the explosion. In [this] depiction, the speech, the explosion, and the riot all take place at once.
21. Greg Krikorian, Evidence emerges in ‘85 Santa Ana slaying, Los Angeles Times, 11 October 2007, B-1.
22. Friedman, Robert I., The California Murder Case That Israel Is Sweeping Under the Rug : Justice: In 1985, Alex Odeh was killed by a pipe bomb in Orange County. The FBI has three suspects, but they are in Israel; extradition is unlikely, Los Angeles Times, 13 May 1990
23. "Rudolph reveals motives". CNN.com. 19 April 2005.
24. Sweden: Stockholm suicide bombings could have been 'catastrophic', London: The Telegraph, 12 December 2010
25. Bojorquez, Manuel (29 October 2018). "Package bomb suspect Cesar Sayoc had list of 100 names in van, official says". CBS News. Archived from the original on 7 February 2019. Retrieved 5 February 2019.
26. "Investigation of Suspicious Packages". Federal Bureau of Investigation. Retrieved 26 October 2018.
27. "FBI Director Christopher Wray's Remarks Regarding Arrest of Cesar Sayoc in Suspicious Package Investigation". Federal Bureau of Investigation. Retrieved 26 October 2018.
28. Benner, Katie; Haberman, Maggie; Schmidt, Michael S. (6 January 2021). "An explosive device is found at the R.N.C., and the D.N.C. is evacuated". The New York Times. ISSN   0362-4331 . Retrieved 7 January 2021.
29. Reilly, Ryan; Kosnar, Michael; Winter, Tom; Dienst, Jonathan; Lavietes, Matt; Schapiro, Rich (4 December 2025). "Suspect arrested in January 2021 D.C. pipe bomb case, DOJ says". NBC News. Retrieved 4 December 2025.

• US5,386,758 –Apparatus and method for disarming pipe bombs