Self Fragmenting Round
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A Stralsund man shot blind and large, and a warlock Finn was he,
And he hit Tom Hall with a bursting ball a hand's-breadth over the knee.
Tom Hall caught hold by the topping-lift, and sat him down with an oath,
"You'll wait a little, Rube," he said, "the Devil has called for both.
The Devil is driving both this tide, and the killing-grounds are close,

(from) The Rhyme of the Three Sealers Rudyard Kipling

Basic Information

A self fragmenting round is a round of firearms ammunition - almost always a small arms round - which is designed to deform or disintegrate on impact with its target or immediately thereafter.

This deformation serves one or both of two purposes: either to increase the magnitude of the damage done to the target or to prevent stray rounds from penetrating lightweight barriers such as internal walls and aircraft skins.

Deforming on target a round creates a larger and more complex wound channel - sometimes tumbling completely off from its original path - and makes it more likely that all of the kinetic energy of the round will be distributed into the target rather than overpenetrating when the round exits.

The deformation of stray rounds serves much the same function, except that the overpenetration that is prevented stops the rounds from damaging unintended targets such as innocent bystanders. This feature also prevents stray rounds from riccocheting off whatever they hit - again, very useful in a close and unfriendly environment.

Many self-fragmenting designs exist - ranging from simple hollow point bullets to small-arms calibre "explosive rounds" and complicated designs like the Glaser Safety Slug1. It is also possible - although not always advisable - to improvise a self fragmenting round by interfering with standard ball, traditionally by cutting a cross-shape into the tip of the round.

The customs and usages of warfare tend to lead most, if not all, militaries to prohibit their personnel from using this kind of ammunition in battle but it is frequently used for civilian purposes (including policing) and against unlawful combattants. As previously noted, it can be extremely useful for purposes such as hostage rescue or for operations in pressurised environments (such as aboard aircraft).

Besides legal/cultural issues it should also be noted that these rounds perform very badly indeed against any form of armour (and, obviously, struggle to penetrate cover as well). Improvised rounds are also frequently bad for the reliability of the weapon from which they are fired and can damage the rifling.


1. full source reference

Game and Story Use

  • In a spacefaring environment, the need to prevent overpenetration (and, indeed, riccochets) should probably lead to a lot more of these.
  • When used in warfare, extreme - and frequently unofficial - retribution is relatively common.
  • Where the RPG system has rules for surgery, consider making treating wounds caused by (some designs of) self fragmenting rounds much harder to fix.
  • Note should also be taken of the performance vs. armour - against, say, a ballistic vest - self-fragmenting rounds may prove more of an annoyance than a hazard.
  • These tend to rely on a target having something internal to damage - the undead, blob monsters, selected shapeshifters, machines and some constructs may be more or less immune.
  • This is a reasonbly good way to deliver your depleted-phlebotinum - wierd materials that would normally play Hob with the action of your weapon can be packaged up inside a nice ballistic jacket and then dispensed as required onto (or indeed into) your target.
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