Is it difficult to determine the caliber of a gun if you don’t have the cartridge casing? I sometimes watch reality shows and noticed they spend a lot of time looking for casings at the crime scene in order to id the shooter’s gun caliber. Can’t then just retrieve the bullet from the victim and find out that way?
The bullet can be mangled and/or fragmented in such a way that might make IDing it’s caliber difficult.
Thanks snfaulkner. And retrieving the bullet at the scene is probably not possible anyway. But if there was a pristine bullet lying next to the victim could someone easily identify the caliber?
Sure.
Even without measuring it, the common calibers (.22, 9mm, .357, .45) are easily identified. If it was something non-obvious, a caliper would do the job quickly.
Bullets fired into things are rarely pristine. But yeah, if you found one, your could just measure it.
ISTM that it would not be difficult to determine the caliber as it pertains to diameter. Even a distorted bullet can be determined to be ~.38" in diameter. But is it a .38 Special? Or is it a .357 Magnum? If it’s jacketed, is it .380 Auto, or 9 mm?
Tough to tell .38 from .357 without the cartridge.
Thanks everyone. Ignorance fought.
Not for nothing, but shell casings are usually good at holding fingerprints, and the scratches in them can be linked to the gun at times.
The same exact bullet (an inert lead lump with usually a copper jacket)is used by multiple calibers (a loaded round with a bullet in a case, with powder and primer behind it). For example, a .308 bullet is used by .308, 7.62x51mm, .30-06, 7.5mm Swiss, .300 Win Mag etc. Even .30-30, though you might be able to tell that they’re normally round nose and the rest (usually) aren’t.
Despite the different names, .357 is the same bullet as .38, it’s just the former is longer and can hold more powder.
For something like 9mm vs .380, you might weigh them and tell whether the bullet weight is too heavy to typically be used in the latter, but it’s not hard and fast.
With just the pulled bullet, it might work best as a diagnosis of exclusion: we know what he didn’t use, but without the case it’s hard to say for certain.
And then, of course, there is the difference between real life and drama to take into consideration.
But even in real life, collecting evidence from the crime scene is needed no matter what, in order to be able to prove what did or didn’t happen.
As for determining the caliber of the weapon, there’s a time factor to consider as well. They certainly aren’t going to dig the bullet out of the body at the scene, so while they can wait for the autopsy, it’s faster to look for casings.
You can identify which gun fired a particular cartridge from the indentations the firing pin makes on the primer.
For example, Glock pistols have a rectangular firing pin so cartridges fired from a Glock 17 are easily distinguishable from those fired from (say) a Beretta M92FS.
Even when you’re dealing with guns with a standard circular firing pin, different firing pins will hit the primer with difference force and in different locations, so it’s still possible to differentiate between cartridges from two guns of the same make and model.
Nobody addressed the unlikelihood of finding a pristine bullet near the body, but it might be possible in the case of a misfire. Bullet doesn’t go bang, shooter works the slide to eject the dud round, and forgets to police his brass before he escapes.
On that same note, semi-automatic and automatic weapons usually will leave behind empty shell casings which can be collected for evidence if the shooter doesn’t clean up effectively.
A bullet is a lump of soft metal that deforms when it hits a solid object, generally after firing the bullet is just a deformed lump of lead if you can even find it. You can tell broadly what cartridge it came from by the size and weight, but it’s not nearly as specific and easy they do on a cop show. And learning ‘it’s about the right size to be a 9mm’ is about as useful as knowing that the getaway car is ‘a 4-wheeled car and not a subcompact, a pickup, or avan’ - you can rule out any kind of rifle, and can know it’s not a .45 or .22, but it doesn’t rule out any of a large set of popular handgun calibers (.380, 9mm, .38 special, .357 magnum) or tell you much about even the basic type of handgun, not even whether it’s a pistol or revolver.
How exactly do you tell the difference between a .38 special and .357 round, or between a 9mm parabellum and .380 ACP round just from the bullet, even it’s not deformed and you have calipers? They use the exact same bullet, just a different size casing behind it.
My understanding is there’s a movement to require gun makers to micro-print the gun’s serial number on the firing pin … so the casing found at the crime scene can be traced back to the exact gun that fired it …
But generally, police are going to collect all the evidence from a crime scene … who knows which little piece will break the case open … the DNA on the cigarette butt matches a felon who just happens to have the victim’s wallet in hand … so police collect all the cigarette butts too … ewwww …
My take on his post is that you can tell the difference between a .45 and a .22, or a .357/.38 and either of those; not that you can determine what variation of the round the bullet was fired from.
[QUOTE=Pantastic;19934863
How exactly do you tell the difference between a .38 special and .357 round, or between a 9mm parabellum and .380 ACP round just from the bullet, even it’s not deformed and you have calipers? They use the exact same bullet, just a different size casing behind it.[/QUOTE]
Or even a 9mm and a .38, since the size is so close.
Diameter is similar, but the commonly used bullet shapes for the two are pretty different. It’s not definitive, and shape takes a beating on impact, but it’s something. Jacketing is another common difference.
Agree with the overall point that determining cartridge type and hence potential models of gun from just an expended bullet dug out of a crime scene is 99% fiction.
Both true. But a clever assassin could load 9mm into one of those Rugers and the cops would be sure it was fired from a semi-auto.