What Degree of Specificity Can a Fired Bullet Reveal the Make and Model of the Gun it Came From?

[SwampWolf]

One thing about the Colt Python is that the barrel has a different twist rate then your average 357 and 38 caliber guns. The Python has a 1 in 14 twist, when you’re other 357s have a 1 in 18 twist rate.

Is the Python rate of twist different from all other Colt revolvers? If it is (and count me doubtful), it would certainly go a long way in validating the opinion of the ballistic experts of the Anchorage, Alaska state police when they determined that the bullet was fired from a Colt Python and only a Python, with great specificity. If the 1 in 14 twist rate is, in fact, unique to the Python, question asked; question answered.

 

[WestKentucky]

I find myself wondering how the availability of aftermarket barrels for certain makes of semi-auto pistols might play into this. I mean someone could buy an aftermarket G-19 barrel, use it for a shooting, then chop up the aftermarket barrel & dispose of it & put the factory barrel back in. That would be a lot of trouble & require planning but it would seem to get around all this.

Not entirely. There’s a lot more to shell casing forensics than what Hollywood lets on. Rifling is the majority of the markings on a bullet, but there are other witness marks from the loading process which will be equally unique. Match a bullet to a barrel and you have a bullet matched to a disposable tube. Match a shell casing to a slide by analysis of firing pin marks, marks from the face of the slide, magazine marks, extractor/ejector markings, and marks where the case gets banged up as it gets ejected… match that up and you have your gun. I have learned a lot by reading the posts on here by @GunnyUSMC and a couple other guys in the field. It’s nice to know how it really works.

 

[Tallball]

Great thread. Thanks to @GunnyUSMC and @Riomouse911 and others for their outstanding and fascinating posts. I'll keep these things in mind when writing mysteries.

 

[21H40]

What about those fancy rifles with progressive rifling or gain twist?

 

[Double Naught Spy]

Is the Python rate of twist different from all other Colt revolvers? If it is (and count me doubtful), it would certainly go a long way in validating the opinion of the ballistic experts of the Anchorage, Alaska state police when they determined that the bullet was fired from a Colt Python and only a Python, with great specificity. If the 1 in 14 twist rate is, in fact, unique to the Python, question asked; question answered.

1:14 twist is not in fact unique to Colt Pythons in .357. So if you only have a bullet and know the twist rate, you don't know what gun it was fired from with any certainty.

Aftermarket TC Contender .357 has a 1:14 TW
https://eabco.com/tc-contender-g2-accuracy-barrel-357-magnum-24-blue-1-14-twist/

From what I am finding online, the Dan Wesson .357 Super Mag also used a 1:14 twist rate, originally, and would fire regular .357 mag rounds.

Freedom Arms .357 mag revolvers also have a 1:14 twist rate from what I have found.

Therefore, if the determination was made that a bullet was fired from a Colt Python, other criteria were used other than just bullet caliber and twist rate.

 

[CDW4ME]

I have a 40 S&W Glock 23C - factory compensated / ported.
I also have a non-ported Lone Wolf 357 Sig barrel for it and it works great.
https://lonewolfdist.com/barrels/gl...phawolf-barrel-for-m-32-357-sig-stock-length/
Assuming a fired 357 bullet came from a pistol originally chambered in 357 might not be correct.

 

[Tallball]

LoL! I doubt if a lot of crimes are committed with Contenders, Pythons, Freedom Arms, etc.

"Yeah Officer, he stuck a $2,000 target revolver in my face, and then ran of with the sixty bucks from the register."

Off topic. Just made me chuckle this morning.

 

[Mk VII]

There are some crooks who will do just that. Most are not the sharpest tools in the box.

 

[Speedo66]

We had a guy chop the barrel and stock on an expensive shotgun worth thousands to do $20 street stickups.

Most street criminals aren’t that smart.

 

[WestKentucky]

The cost of a stolen gun is the same no matter what it’s worth. When the mindset is free tool then it just gets used like any other tool. An unfired gold plated jeweled and inlayed gold cup national match or a spray painted dog chewed hi-point is the same thing… a gun. And with that gun, criminals can do various crime.

 

[The Night Rider]

I watched a documentary once on the battle of the Little Bighorn in which the investigators were able to take guns known to have been used in the battle and match specific bullets found on the field with a metal detector to those guns.

They then used that data to extrapolate where the guns moved on the field. I think they were also able to do that with shell casings

 

[GRIZ22]

LoL! I doubt if a lot of crimes are committed with Contenders, Pythons, Freedom Arms, etc.

"Yeah Officer, he stuck a $2,000 target revolver in my face, and then ran of with the sixty bucks from the register."

Off topic. Just made me chuckle this morning.

Criminals usually don't care how valuable a stolen gun they buy on the street is. They usually don't care what it's loaded with either. I've seen revolvers with a different brand and bullet shape in each chamber. Also semi autos with 3 or 4 different rounds in the magazine.

 

[wolf695]

Firing pin strike and barrel rifling, most times tell the tale of what weapon was used! But not always!

 

[Double Naught Spy]

I have never seen a firing pin strike on a bullet, the original concern of the OP.

 

[Hooda Thunkit]

Criminals usually don't care how valuable a stolen gun they buy on the street is. They usually don't care what it's loaded with either. I've seen revolvers with a different brand and bullet shape in each chamber. Also semi autos with 3 or 4 different rounds in the magazine.

The former owner of a now-closed LGS told me of a young thuggish-looking (his description) guy that came in one evening wanting to purchase a magazine full of ammo.
He didn't want a full box of 50, or even 20 rounds, just enough to top off his magazine. He didn't know or care what the ammo was that fit his gun, he just wanted the 12 or so "caps" to fill it.

The owner of the LGS started closing earlier, and eventually just retired.

 

[Zahn]

I'm sure firearm forensic experts see some interesting things.

Like someone firing 9mm cartridges in a .40 S&W. Heck, maybe it was fired from a 10mm. I'm no expert.

 

[GunnyUSMC]

I'm sure firearm forensic experts see some interesting things.

Like someone firing 9mm cartridges in a .40 S&W. Heck, maybe it was fired from a 10mm. I'm no expert.

View attachment 1157953

I worked a case there a guy was shooting 9mm from a S&W M&P 40. I matched up several shootings from the cartridge cases. I started test firing 9mm in the M&P 40s that were recovered. I ended up matching a M&P 40, that was taken off a drug dealer, to the shootings.

 

[GunnyUSMC]

Great thread. Thanks to @GunnyUSMC and @Riomouse911 and others for their outstanding and fascinating posts. I'll keep these things in mind when writing mysteries.

Check to see if there’s a Crime Lab in your area. If so, contact their firearms division and see if they will let you go by for a visit.

 

[GunnyUSMC]

1:14 twist is not in fact unique to Colt Pythons in .357. So if you only have a bullet and know the twist rate, you don't know what gun it was fired from with any certainty.

Aftermarket TC Contender .357 has a 1:14 TW
https://eabco.com/tc-contender-g2-accuracy-barrel-357-magnum-24-blue-1-14-twist/

From what I am finding online, the Dan Wesson .357 Super Mag also used a 1:14 twist rate, originally, and would fire regular .357 mag rounds.

Freedom Arms .357 mag revolvers also have a 1:14 twist rate from what I have found.

Therefore, if the determination was made that a bullet was fired from a Colt Python, other criteria were used other than just bullet caliber and twist rate.

Another thing about the Python is, the rifling at the end of the barrel had a slight taper. This was done to improve accuracy. It also reduced the caliber size of the bullets.
I would have to check with one of my Firearms Examiner friends, to see if there’s something about the Python, other the rate of twist and the tapered bore, that would make it unique.

 

[Carl N. Brown]

The two groove barrels of some WWII Springfield 1903 bolt actions are very distinctive.

 

[Jim Watson]

I think most other Colts are 16 twist 6 groove, Smiths are typically 18.75 twist 5 groove.
One left, one right I forget which.
But manufacturers change their minds, you would need a running accumulation for a teevee CSI lab.

 

[Mk VII]

Marlin Microgroove rifling caused something of a stir when it was first introduced, some people asserting that it would be impossible to trace bullets engraved by it. It proved to be no less amenable to such techniques than any other.

 

[Anchorite]

Interesting comment thus far. I’ll add the following link to an excellent recent article on the subject for those so inclined to dive deeper into the subject.


https://radleybalko.substack.com/p/devil-in-the-grooves-the-case-against?utm_medium=email

I can tell you that those of us who routinely try cases to juries - be it a civil or criminal case - are always dealing with these issues.

 

[Jim Watson]

Comic strip detective Kerry Drake was framed by someone who managed to secure a bullet fired from his .38, patched it, and fired it from a smoothbore dueling pistol to eliminate a competing mobster.

 

[Mk VII]

The Shirley McKie case hinged on the certainty of identification of fingerprint evidence by examiners at the Scottish Criminal Record Office, who continue to maintain that their identification was entirely correct. https://en.wikipedia.org/wiki/Shirley_McKie