# Gun Caliber Identification **URL:** \ **Category:** Factual Questions\ **Created:** [January 20, 2017, 2:12am UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595 "2017-01-20T02:12:22Z")\ **Posts on this page:** 11\ **Page:** 2
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [January 20, 2017, 8:23pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/21 "2017-01-20T20:23:32Z")
> [@LSLGuy](#): > > 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. Specifically, .38 Spl is more likely to have odd shapes. You aren’t likely to find [wadcutter or semiwadcutter](https://en.wikipedia.org/wiki/Wadcutter) 9mm - the shape doesn’t load properly from a magazine. They do make 9mm revolvers that could theoretically use WC, but I’ve never seen them sold in that shape (you could load your own if you really wanted to). 9mm is also more likely to be jacketed (though exceptions exist), while .38 can be commonly jacketed or lead. ---
**Author:** ![Orwell](https://avatars.discourse-cdn.com/v4/letter/o/dfb087/32.png) [@Orwell](https://boards.straightdope.com/u/Orwell)\ **Post date:** [January 20, 2017, 10:06pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/22 "2017-01-20T22:06:43Z")
> [@Pantastic](#): > > 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. Indeed. What makes me shake my head even more is when a TV cop or CSI looks at a wound on a body and says “he was shot with a 9mm”, and then another says “that’s the same caliber as the clown shooting last week. Must be the same guy.” First off, there is no way a cop or CSI can look at a wound and tell what caliber gun was used. Even if they could, 9mm is the same diameter as the calibers mentioned in the post above, so you’re sure he wasn’t shot with a .38 special or .380? And even if it was a 9mm, that is probably the most common caliber of pistol used in the world. Does that really narrow it down much for you super-cops? But in the end, even examining most bullets with a microscope to look at rifling marks is often far from conclusive in matching a bullet with a specific firearm. Especially if the bullet is deformed, which often happens. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [January 20, 2017, 10:29pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/23 "2017-01-20T22:29:32Z")
> [@Orwell](#): > > Indeed. What makes me shake my head even more is when a TV cop or CSI looks at a wound on a body and says “he was shot with a 9mm”, and then another says “that’s the same caliber as the clown shooting last week. Must be the same guy.” > > First off, there is no way a cop or CSI can look at a wound and tell what caliber gun was used. Even if they could, 9mm is the same diameter as the calibers mentioned in the post above, so you’re sure he wasn’t shot with a .38 special or .380? And even if it was a 9mm, that is probably the most common caliber of pistol used in the world. Does that really narrow it down much for you super-cops? > > But in the end, even examining most bullets with a microscope to look at rifling marks is often far from conclusive in matching a bullet with a specific firearm. Especially if the bullet is deformed, which often happens. I have heard real life forensics use the terms “large caliber” and “small caliber”. And, from the couple times they let me look at a body, a .22 make a rather small hole. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [January 20, 2017, 10:35pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/24 "2017-01-20T22:35:58Z")
In\* Hell on Wheels\*, there is a funny bit that is major plot point. Our protagonist carries a rather rare Griswold & Gunnison .36 caliber percussion revolver. [Civil War Pistol; Griswold & Gunnison Confederate Percussion Revolver](http://www.gunclassics.com/griswold.html) Now, yeah, you could be recognized by that gun. But the plot point is that some Pinkerton finds a dead body, digs the balls out, and determines that they are from a Griswold & Gunnison!:eek: And is thus on the track of the protagonist. Sure, he’d be able to get a .36 caliber percussion revolver from the balls, but never, \*ever \*what company made it. ---
**Author:** ![Orwell](https://avatars.discourse-cdn.com/v4/letter/o/dfb087/32.png) [@Orwell](https://boards.straightdope.com/u/Orwell)\ **Post date:** [January 20, 2017, 10:43pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/25 "2017-01-20T22:43:59Z")
> [@DrDeth](#): > > I have heard real life forensics use the terms “large caliber” and “small caliber”. And, from the couple times they let me look at a body, a .22 make a rather small hole. Yeah, I believe that. A .22 or .25 is much smaller and lower power than the 9-10 mm or .38-.45 calibers. Of course, the .22 rifle calibers like .223 have much more power than a .22lr, and would make different wounds. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [January 21, 2017, 3:05am UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/26 "2017-01-21T03:05:47Z")
Granted, the deformed aspect of a spent round makes identification more difficult without the benefit of the additional information a corresponding casing would provide, and the depictions portrayed on TV and the movies are far from accurate… But the notion that certain groups of firearms utilize the same bullets (.38, .357, 9mm, .380, etc., etc.) is far from true. Barring handloaded semi-wildcat rounds, and certain **rare** commercial exceptions… They may be **close** but are **not** the same, and are **not** interchangeable. Generally speaking, the weight and dimension(s) vary noticeably from one to another. The rifling and force cone marks, etc., further help to identify the weapon manufacture, and consequentially the caliber. So ID is not nearly as impossible as some here have implied. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [January 21, 2017, 6:39am UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/27 "2017-01-21T06:39:20Z")
.38/.357 bullets are .002 inches wider than 9mm in their typical loading, and are labeled differently. While reloading, generally you stick to this pattern, barring some calibers where you match the bullet diameter to the bore after careful measurement (e.g. 7.62x54R). ---
**Author:** ![Pantastic](https://avatars.discourse-cdn.com/v4/letter/p/3bc359/32.png) [@Pantastic](https://boards.straightdope.com/u/Pantastic)\ **Post date:** [January 21, 2017, 10:31pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/28 "2017-01-21T22:31:04Z")
> [@ZurBob](#): > > Granted, the deformed aspect of a spent round makes identification more difficult without the benefit of the additional information a corresponding casing would provide, and the depictions portrayed on TV and the movies are far from accurate… > > But the notion that certain groups of firearms utilize the same bullets (.38, .357, 9mm, .380, etc., etc.) is far from true. Barring handloaded semi-wildcat rounds, and certain **rare** commercial exceptions… They may be **close** but are **not** the same, and are **not** interchangeable. Generally speaking, the weight and dimension(s) vary noticeably from one to another. The rifling and force cone marks, etc., further help to identify the weapon manufacture, and consequentially the caliber. So ID is not nearly as impossible as some here have implied. I don’t know where you’re getting your information, but it’s wrong. It’s completely true that certain groups of cartridges use the same bullets. .38 special and .357 magnum (along with a few other more obscure calibers) use the exact same size bullets, there’s no difference even in the specifications. Same with some other families like 9mm Parabellum (the standard ‘9mm’) and .380 auto. They aren’t just close, they are the same - for a cite, people who sell molds for making bullets sell them based on the family, they don’t have a ‘.38 but not .357’ mold. [http://leeprecision.com/bullet-casting/hand-gun-bullet-molds/](http://leeprecision.com/bullet-casting/hand-gun-bullet-molds/) For a lot of these, even cartridges are interchangeable as long as you’ve got a gun rated for the highest pressure round - a .357 revolver can fire .38 special rounds, and a .44 magnum can fire .44 special rounds, and it’s often done to save money for practice ammunition. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [January 21, 2017, 10:39pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/29 "2017-01-21T22:39:34Z")
> [@snfaulkner](#): > > Bullets fired into things are rarely pristine. But yeah, if you found one, your could just measure it. The Kennedy gurney bullet? ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [January 21, 2017, 10:41pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/30 "2017-01-21T22:41:56Z")
> [@White SIFL](#): > > The Kennedy gurney bullet? It only seems pristine when photographed from one particular angle. Other angles make its deformation instantly obvious. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [January 22, 2017, 1:09pm UTC](https://boards.straightdope.com/t/gun-caliber-identification/777595/31 "2017-01-22T13:09:50Z")
> [@Pantastic](#): > > I don’t know where you’re getting your information, but it’s wrong… Wow,:eek: you’re absolutely right. I was _nitpicking_ around the edges in an attempt to make a broad statement… It didn’t work. Dickslap accepted. BTW, info from Lyman’s #48 (obviously read in the dark) [Previous page](https://boards.straightdope.com/t/gun-caliber-identification/777595.md?page=1)