I have seen this in a lot of movies and noticed it again now in "Taxi Driver". There is a scene where Robert De Niro cuts an 'X' into his pistol rounds with a knife.

I don't know much about weapons, is there any technical reason to do this? Does it somehow improve the ammunition? Does he do that to open up the round?

Or does it have some symbolic reason, like marking the ammunition in a personal way? What is this kind of scene usually supposed to tell the viewer? Is there any special meaning?

cutting scene from Taxi Driver


3 Answers 3


Cutting a round in this way guarantees that the round will fragment upon striking the body creating more severe wounds. There is the forum post Is it illegal/unwise to modify pistol ammo? with ammunition specialists answering a similar question.

Bottom line: While it is not illegal to modify the rounds (though the MURDER is illegal), don't do it unless you know what you're doing since inaccuracy can cause you to lose some of your own body parts, because it may fragment even before it leaves the gun barrel causing blockage and/or explosion.

For those looking into the forum entry I listed above, a lot of acronyms abound. I found the translations of the first few:

  • JSP - Jacketed Soft Point
  • JHP - Jacketed Hollow Point
  • FMJ - Full Metal Jacket
  • HP  - Hollow Point
  • LRN - Lead Round Nose
  • Great, thanks! So I suppose they put this kind of scene in a movie to tell us that the character is really tough, determined and knows what he is doing, right?
    – magnattic
    Commented Mar 4, 2012 at 13:10
  • 4
    At least the tough and determined part.
    – wbogacz
    Commented Mar 4, 2012 at 14:51
  • 3
    "... guarantees that the round will fragment upon striking the body..." one should be careful with such definite statements (especially if the source is a internet forum, whose posting members may or may not actually be "ammunition specialists"). - A similar question has been posted at our StackExchange sister site Skeptics.
    – Oliver_C
    Commented Oct 13, 2015 at 9:07
  • Very rarely do screen writers "know what they are doing" with respect to technical details; it's almost always a caricature or trope of some kind to imply or signal something. Invariably, they get it wrong. See also Ronin, where DeNiro's character bitches about bullets being "sprayed with teflon" to make them armor piercing.
    – nyet
    Commented May 1 at 21:22

The shooting script (no pun intended) describes this as 'dum-dumming'.

He sits at the table dum-dumming the .44 bullets -- cutting "x's" across the bullet heads.

Per wikipedia ("Expanding Bullet")

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

  • Note that expanding bullets are illegal in warfare per the Hague Convention of 1899, but are legal for other uses.
    – dan04
    Commented Dec 11, 2023 at 20:30
  • One of the advantages to expanding bullets is preventing over penetration (e.g. walls). The "humane" "convention" against hollow points makes zero sense, but makes good pablum material for alarmists.
    – nyet
    Commented May 1 at 21:20

It does nothing - I have done this myself for hunting. It's just a tough thing to do without any results. If he got himself a cordless drill and drilled the bullet in by 3 or so millimeters, then it's a hugely different story, as then the bullet will expand by approx 3 times the size, which is what's wanted when hunting, so that the game comes down fast and the kill is fast, clean, and humane.

  • 1
    Hey - is there any chance you could give us some source material, as well as your personal experience? And out of curiosity, what do you mean when you say that, "it's a tough thing to do without any results"? Thanks!
    – ghostdog
    Commented Oct 13, 2015 at 0:05
  • 3
    I think he means it's alot of work cutting them, for nothing to show for it. Drilling the bullets turns them into hollow points, on the other hand. And ianal but is that even legal?
    – cde
    Commented Oct 13, 2015 at 0:31
  • @cde: It is. You can make your own ammo so you can modify ammo. The only question is if the resulting round would be legal, and you can buy them just fine so it is.
    – Joshua
    Commented Mar 27, 2017 at 16:21
  • Also, if I don't misunderstand you american's weapon laws, "legal to own and shoot" does not always imply "legal to use to hunt an animal with"? Commented Dec 12, 2017 at 23:19
  • Legality isn't really at issue here. The issue is whether or not this actually accomplishes anything other than misinforming the public in the service of a marginally interesting trope.
    – nyet
    Commented May 1 at 21:24

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