Expanding bullets, also known colloquially as dumdum bullets, are projectiles designed to expand on impact. This causes the bullet to increase in diameter, to combat over-penetration and produce a larger wound, thus dealing more damage to a living target. For this reason, they are used for hunting and by most police departments, but are generally prohibited for use in war. Two typical designs are the hollow-point bullet and the soft-point bullet.
Leg wound by a dumdum bullet
Composite image of the British Medical Journal article describing Capt Bertie-Clay's new type of bullet (British Medical Journal 1896;2:1810)
German WWI propaganda: French Dum-Dum bullets (c. 1916)
Expanded .458 hunting round (next to a Ugandan 500-shilling coin [23.5 mm diameter] for size reference), after killing an African buffalo
A hollow-point bullet is a type of expanding bullet which expands on impact with a soft target, transferring more or all of the projectile's energy into the target over a shorter distance.
.357 Magnum rounds. Left: Jacketed soft-point (JSP) round. Right: Jacketed hollow-point (JHP) round. JSP is a semi-jacketed round as the jacket does not extend to the tip
Various hollow points: .45 Auto, .38 Special, .44 S&W Special, .44 Remington Magnum
.45 ACP Federal HST 230gr hollow point cartridge, with two rounds of CCI Standard Velocity .22 LR for comparison purposes
.40 S&W round, complete cartridge and expanded bullet
![Expanded .458 hunting round (next to a Ugandan 500-shilling coin [23.5 mm diameter] for size reference), after killing an African buffalo](https://upload.wikimedia.org/wikipedia/commons/thumb/a/ad/Expanding_bullet_after_firing.jpg/640px-Expanding_bullet_after_firing.jpg)
