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Drawings from 1870 of a hollow point express rifle bullet before firing (1, 2) and after recovery from the game animal (3, 4, 5), showing expansion and fragmentation.

In the field of firearms, an expanding bullet is a bullet designed to expand on impact, increasing in diameter to limit penetration and/or produce a larger diameter wound. There are many expanding bullet designs, though the most commonly encountered are the hollow point bullet and the soft point bullet.



Such bullets are sometimes known as Dum-dum or dumdum bullets, after an early British example produced in the Dum Dum Arsenal, near Calcutta, India by Captain Neville Bertie-Clay.[1][2]. There were several expanding bullets produced by this arsenal for the .303 British cartridge, including soft point and hollow point designs. These were not the first expanding bullets, however; hollow point expanding bullets were commonly used for hunting thin skinned game in express rifles as early as the mid 1870s.[3]. The use of the term "Dum-dum", applied to expanding bullets other than the early .303 designs, is considered slang by some.[4] Manufacturers have many terms to describe the particular construction of the various types of expanding bullets, though most fall into the category of soft point or hollow point designs.


Early bullets were typically made in the form of spheres of nearly pure lead, which is a very soft material. These would often flatten upon impact with the target, causing a larger wound than the original diameter of the ball. The adoption of rifling allowed the use of longer, heavier bullets, but these were still typically constructed of soft lead and would often double in diameter upon impact. In this case expansion was a side effect of materials, and there is no evidence that the bullets were designed to expand upon impact.[5]

The earliest examples of bullets specifically designed to expand on impact were those fired by express rifles, which were developed in the mid 19th century. Express rifles used larger powder charges and lighter bullets than typical for the time to achieve very high velocities for black powder cartridges. One method of lightening the bullets used was to provide a deep cavity in the nose of the bullet. These were the first hollow point bullets, and in addition to developing higher velocities, they also expanded significantly upon impact. These hollow point bullets worked well on thin-skinned game, but tended to come apart on bigger game, resulting in insufficient penetration. One solution to this was the "cruciform expanding bullet", a solid bullet with an X shaped incision in the tip. This split section expanded to the depth of the incision, and then stopped, making it an early form of controlled expansion bullet.[6]

In the late 19th century, the invention of Cordite and other nitrocellulose based "smokeless" propellants permitted higher velocity than black powder, along with flatter trajectories and correspondingly higher hit probabilities. However to limit the amount of recoil to an acceptable level meant that higher velocity rounds needed lighter (and thus smaller diameter) bullets.

Soon after the introduction of smokeless powder to firearms, full metal jacket bullets were introduced to prevent lead fouling in the bore caused by the higher pressures and velocities when used with soft lead bullets.[7] However, it was soon noticed that such small caliber rounds were less effective at wounding or killing an enemy than the older large caliber soft lead bullets. Within the British Indian Army, the Dum Dum arsenal produced its now infamous solution - the jacketing was removed from the nose of the bullet, creating the first soft point bullets. Since the Mark II jacket did not cover the base of the round this could potentially lead to the jacketing being left in the barrel. This potential problem resulted in the rejection of the Dum-dum design, and independent development of the Mark III, Mark IV (1897) and Mark V (1899) .303 British rounds, which were of the hollow point design, with the jacket covering the base; while these were made in Britain, not at the Dum-Dum arsenal, the name "Dum-dum" had already become associated with expanding bullets, and continued to be used to refer to any expanding bullets. The expanding bullets expanded upon impact to a diameter significantly greater than the original .312 inch (7.62 mm) bullet diameter, producing larger diameter wounds than the full metal jacketed versions. The Mark IV was successful enough in its first use at Omdurman that British soldiers issued with the standard Mark II bullets began to remove the top of the jacket, converting the Mark II bullets into improvised Dum-dum types.[8]

In 1898, the German government lodged a protest against the use of the Mark IV bullet, claiming the wounds produced by the Mark IV were excessive and inhumane, thus violating the laws of war. The protest, however, was based on the comparison of the wounds produced by expanding and non-expanding bullets from high velocity sporting rifles, rather than a comparison of the expanding .303 British bullets with the previous, large bore service cartridge it replaced, the .577/450 Martini-Henry.[9] Because the energy was roughly the same, the wounds caused by the expanding bullet of the .303 were less severe than the those caused by the larger caliber, solid lead bullet used by the Martini-Henry.[10]

The German protests were effective however, resulting in the ban of the use of expanding bullets in warfare. The British replaced the hollow point bullets with new full metal jacket bullets, and used the remaining stocks of expanding bullets for practice.[11]


The Hague Convention of 1899, Declaration III, prohibits the use in international warfare of bullets which easily expand or flatten in the body, giving as example a bullet with a jacket with incisions or one that does not fully cover the core.[12] This prohibition was an expansion of the Declaration of St Petersburg in 1868, which banned exploding projectiles of less than 400 grams. During the Convention, representatives from Imperial Germany provided evidence of severe expansion in flesh, however these experiments were severely criticized by the British because they used higher powered German sporting cartridges with expanding bullets, and compared results only to the earlier, non-expanding .303 bullets. No comparison was made with the terminal effects of the non-jacketed, large bore bullets used just a few decades before by militaries around the world, such as the .577 caliber (14.7 mm) Snider-Enfield and the .45 caliber (11.4 mm) Martini-Henry which the .303 replaced.[13]

Because of the greater effectiveness in disabling or killing the target, the use of expanding rounds remains legal, or even required, in some circumstances. Examples of this are use of appropriately expanding bullets in hunting, where it is desirable to stop the animal quickly either to prevent loss of a game animal, or ensure a humane death of vermin, and in law enforcement or self defense, where quickly neutralizing an aggressor may be needed to prevent further loss of life.[14][15]

See also


  1. ^ "Dum Dum". Encyclopædia Britannica. 2009. Retrieved 2009-05-18. 
  2. ^ "DUM-DUM CARTRIDGES.". The New York Times. January 4, 1886. 
  3. ^ Arthur Augustus Thurlow Cunynghame, M. Balkind, (1880). My Command in South Africa, 1874-1878. Macmillan & Co.. p. 79. 
  4. ^ "MidwayUSA GunTec Dictionary". 
  5. ^ Townsend Whelen (1918). The American Rifle. Century Co.. pp. 364–366. 
  6. ^ William Wellington Greener (1885). The gun and its development. Cassell. pp. 223–224. 
  7. ^ "lead fouling". Midway USA GunTec Dictionary. 
  8. ^ "Dum Dums". 
  9. ^ International Arbitration and Peace Association (August, 1899). "The Defence of the Dum-dum". Concord (Published by T.M. Ndze): 129.  "I speak of the experiments made at Tubingen by Prof. Bruns, of which a report has been published in the Beitrage zur Klinischen Chirurigie at Tubingen in 1898. The ball then used had a lead point almost a diameter longer than the case, and, consequently, the expansion and flattening in penetrating a body were considerable, and the wounds excessively severe."
  10. ^ Parliamentary Debates: Senate and House of Representatives author=India Parliament, New South Wales Parliament, Australia Parliament, Legislative Council, Parliament, Victoria. Commonwealth Govt. Printer.. 1903. p. 4227.  "In the dum-dum bullet the jacket ends by leaving a small piece of the core uncovered. The effect of this modification is to produce a certain extension or convexity of the point, and to give a force more pronounced than that of a bullet which is completely jacketed, at the same time, however, less effective than that of the Enfield, Snider, or Martini bullets, all of which have greater calibre."
  11. ^ "REJECTED MARK IV. BULLETS.". , "These bullets have been made up into cartridges, which are being used for practice purposes."
  12. ^ Hague Convention Declaration III - On the Use of Bullets Which Expand or Flatten Easily in the Human Body July 29, 1899
  13. ^ "Dum Dums". 
  14. ^ "Dum-dum Ammunition". 
  15. ^ J A ULERY (OCTOBER 1975). "HOLLOWPOINT AND LAW ENFORCEMENT". Police Chief 42 (10). 

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