whalelovers2000 asked:
During the process of loading, firing and re-loading, the firearm experiences several mechanical events that imparts markings to the projectiles and cartridge cases. Discuss what we typically can expect to find after close examination of these items.
Melinda
During the process of loading, firing and re-loading, the firearm experiences several mechanical events that imparts markings to the projectiles and cartridge cases. Discuss what we typically can expect to find after close examination of these items.
Melinda
June
Magazines can score the brass as it’s slid into place.
Ejecting the shell can leave a “grab” mark on the shell as the round is ejected.
The expanding gas causes a shell to get a might fatter in the middle, reducing its life to about three reloads.
A question on reloading gets ballistics and forensics information
brillant.
Javier
It is called the study of ballistics. The rifling marks on the bullet itself and the markings left on the shell casings by the firing pin and other parts of the gun.
Ballistic markings on a firearm are just like finger prints. No two guns markings are the same.
Lloyd
Greetings. scratches on the cartridge case from the loading where it was forced into the chamber. the firing pin indentation from when it was fired. the extractor contact area where the empty was extracted or pulled out of the chamber. and if you find the cases then you know pretty well that they were fired by a semi automatic firearm and not a revolver, since a revolver does not kick out the empties.
Beth
Forensics 101?
1) Firing pin impressions on primer cap
2) on semi-automatics- casing scars from the ejector clip.
3) rifling scores on the bullet
4) indents from the reloading vise on the shell
5)scars on the bullet from the reloadind press
6) possible trace contamination of bullet and/or shell from previous rounds fired
Anthony
you mean the shell casings? they could be dented, burnt, scratched, etc. physical damage to the sheel happen on every single casing fired….
Bonnie
Loading a cartridge involves the use of several tools, each of which may leave microscopic tool marks on the brass. A typical pistol cartridge may go through 3 dies, not to mention use of a primer pocket reamer and a case mouth reamer/deburring tool, and there’s even a deburring tool for new cases used to debur the inside of the primer pocket.
From the loading bench to the firearm, there are all sorts of random scratches that can occur but aren’t really part of your question.
When the cartridge goes into the firearm, additional scratches, most random, can also occur. When the cartridge is fired, there’s an imprint of the firing pin on the primer, which may also be flattened and in some cases may even rupture or back partway out of the case (these only in overly “hot” handloads). The case head expands, usually less than .001″, and the more forward parts of the case expand to, but not necessarily all the way to, the dimensions of the chamber, where more tool marks could in theory be imprinted. The extractor and ejector mechanisms may also leave marks.
The bullet, if it’s a solid as used in elephant hunting, is imprinted with rifling marks and microscopic tooling marks as it travels down the barrel, and may be largely undisturbed after it hits its target, but even heavily constructed bullets with a thick, hard jacket and a softer, denser core may rivet or otherwise deform if they hit something hard enough. Less sturdily constructed bullets may not fare so well when they get where they’re going, and may even to a large degree disintegrate.
I suppose it’s all forensically interesting to a degree, but if I were a criminal, I’d certainly not be caught with any evidence from such silliness. It’s too simple to polish the surfaces and change the marks. I think MD, for instance, has gone to the futile extreme of requiring handguns be ballistically “fingerprinted” before sale, and I’d be willing to bet money it rarely if ever helps solve a crime.