TexasCHLforum.com

http://www.foxnews.com/story/0,2933,408781,00.html

The link is the story of the two girls murdered in oklahoma. LE is now saying one of the guns used was a Glock .40. They do not have the gun. The story does not elaborate on HOW they know it was a Glock.

So here is the question. How can they determine that it was in fact a Glock? Assuming that all they have to go on is the wounds, and/or maybe a couple shell casings.

Does a Glock make a distinctive marking on the casing? Primer dent? How do they know?

Rectangular primer dent.

Also discussed here, with a link to a post with pictures of the difference. http://www.texasshooting.com/TexasCHL_F ... =9&t=18289

That was my picture. Here it is:


HK USP Compact primer strike on the left, Glock primer strike on the right. I was kind of freaked out about it at first, but wiser heads than I on this board assured me that this is normal for a Glock primer strike.

this was an area of contention with the early models of S&W Sigma, as it had a similar firing pin.
I believe Glock sued'em, and in turn, the Sigmas began coming out with a different firing pin, so yeah, Glocks leave a distinct firing pin mark in the primer.

all of the above info was gleaned from this site, so I trust it's authenticity.

Plus the ballistics would show octagonal rifling on the bullet.

gregthehand wrote:Plus the ballistics would show octagonal rifling on the bullet.

there are other guns with octagonal rifling.

mr.72 wrote:

gregthehand wrote:Plus the ballistics would show octagonal rifling on the bullet.

there are other guns with octagonal rifling.

There are no other guns that have the rectangular primer strike and polygonal rifling. Except perhaps, of course, the early Sigmas.

Xander wrote:

mr.72 wrote:

gregthehand wrote:Plus the ballistics would show octagonal rifling on the bullet.

there are other guns with octagonal rifling.

There are no other guns that have the rectangular primer strike and polygonal rifling. Except perhaps, of course, the early Sigmas.

Actually, some of the Kahr pistols (also available in .40 cal) have a polygonal rifled barrel and the primer strike (as noted on page 20 of their manual) is often times elongated and looks similar to the Glock (see artists rendering).

http://www.kahr.com/DL/kahrmanual.pdf

While I doubt a Forensic Firearms tech would be fooled, a layman (police) might be mislead into making assumptions.

I don't know enough about this to comment, but TAM's photo displays not so much the distinct firing pin impression as the "firing pin drag." All firing pins remain in contact with the primer for a moment after the strike, and design and mechanics dictate if there's a perceptible drag mark resulting from the movement of the cartridge in relation to the firing pin. Mechanically tight revolvers and bolt-action rifles won't show any drag marks, but most autoloading pistols do. Glocks happen to have a pretty deep and distinctive "drag."

Similarly, the way the cartridge and mechanism behave together also affects the extractor markings. You can have essentially the same shape and size extractor claw on two types of firearms, but the same actions at combustion and recoil that create distinctive primer drags can create extractor claw shift and drag, as well.

Another item used in identifying cases are markings made on the case's exterior when it expands at combustion to press against the chamber. If you doubt the force of this pressure, just shoot a .40 S&W round in a .45 ACP pistol (no, don't; but if you've ever seen one you know how much expansion pressure there is against chamber wall). Certain factory barrels can have tell-tale etchings that mark the case in a distinctive way.

And in an autoloader, the cartridges are stripped from the magazine, shoved into the chamber (generally up a barrel ramp), pulled back out again by the extractor, and bumped loose and thrown from the slide by the ejector. The brass does a lot of slippin' and slidin'. Evidently, some firearms leave marks that can be distinguished from others. For example--the way I understand it--the same brand of ammunition fired from my 1911 carry gun will have distinctive marks along the brass compared to that fired from my XD45.

I used to know a guy in California who worked in forensics, and I thought stuff like this was fascinating. Techniques and the library of data must be vastly improved now.

all crimes aside...what woul happen if you fired a .40 thourgh a .45?

ironsights wrote:all crimes aside...what woul happen if you fired a .40 thourgh a .45?

in a glock the case would expand to fit, you would have a light shot and it wouldn't be accurate

I have a case of a 44 S&W SPC (We don't own a gun to shoot it) where I guess it was shot in a 45 long colt and it just looks like a shouldered case except it goes outward instead of inward.

But you shouldn't do it unless you absolutely have to (which probably has only happened twice or so in human history)