Talk:Ballistic fingerprinting
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[edit] Toolmark Identification
I remember hearing G. Gordon Liddy back in 2000 talk about "ballistic fingerprinting". He said that a more correct term for this would be "Toolmark Identification".
Perhaps the proper name for the article should be something like "Firearm Toolmark Identification" or something along those lines.
It would be a better term than "ballistic fingerprinting" (especially given the fact that guns do not have fingers.)
69.39.172.17 05:35, 16 February 2006 (UTC)
- Although Google is not a definite source, I find considerable listings for "ballistic fingerprinting". Toolmark identification might be more accurate, but is not evidenced on Google as being the terminology presently used. Yaf 06:00, 16 February 2006 (UTC)
It had never been called "ballistic fingerprinting" to those in the discipline. In the 1930s, it was called "forensic ballistics" for a while. Now it is called "firearms examination." The matching of cartridge cases and/or bullets to specific weapons is "firearms identification." While bullet striae, breech face impressions on primers, extractor marks, and ejector marks are technically toolmarks, one doesn't want to get into all the burglary pry mark matches and so on that make up the field of toolmark identification, at least not under this heading.
For more information, see:
Association of Firearm and Toolmark Examiners
Relatively new to Wikipedia, so I don't want to go off on a tear and edit anything, but I feel something should be noted in this article.
With modern machinery and mass production of barrels, thousands of firearms will impart the same "ballistic fingerprint" to a fired cartridge.
Firearms manufacturers don't make barrels one at a time. For example, a production run of 5000 Glock 17 9mm handguns will have barrels produced in the same run, and, conceivably, if using the same make of ammunition, all 5000 pistols will impart a virtually identical "ballistic fingerprint" to the fired round.
A "ballistic fingerprint" could potentially be used to determine whether a round was fired from a particular make or model of firearm, to be sure - not a point I'd argue.
Kythri 11:46, 03 April 2006 (UTC)
not true because each of the guns would have to have barrles that are exacly the same down to micrometer of all measurments of not only the barrel but the entire gun, the mag/bolt/casing/rifiling/muzzle all can leave marks on the gun, not to memtion that the tools that glock use are not high quality so there will be sloppy manufacturing. there is a chance that you could have the same fingerprint as someone else but the chanse is so high that its not even worth mentioning
- On what basis do you say the tools Glock uses are not high quality? Jtrainor 22:57, 16 August 2006 (UTC)
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- Have you looked at a Glock pistol? It's a military arm, made primarily of injection molded plastic, and stamped and welded sheet metal. The barrels are hammer forged; this requires a million dollar tool, but spits out a rifled, chambered, profiled barrel in a single step ever 30 seconds or so, and if you can afford the machine, it is by far the cheapest barrel making tool in the long run. Being a military arm, it's designed to be cheap and "good enough". It is NOT designed to have micrometer tolerances, because if it did, it would cost 10x as much and be horribly unreliable. Just look at the AK-47's legendary reliability, all due to loose tolerances. If you want high quality, take a look at the benchrest shooting game. Reliability is not an issue, precision and repeatability are everything. Those guys consider a barrel with more than a thousand rounds fired through it shot out... scot 14:46, 6 October 2006 (UTC)
Loose clearances, if it had loose tolerances, it would fail or destroy itself due to chamber varations. The AK has loose clearances due to a deliberate engineering decision.
I removed the phrase about current production Ar's having a 1/7 twist. This is nonsense. Most civilian AR's are currently produced with 1/9 twist barrels. Almost all Bushmasters are 1/9 and they are far and away the largest civilian producer at the moment as Colt is largely metting governemnt orders at this time. Colt's current share of the civilian market is very small froma historic standpoint according to current ATF production data. Armalite and CMT/Stag also mainly manufacture rifles with a 1/9 twist barrel.
There are still a large minority of AR's made with 1/7 and 1/8 twist barrels. Almost every twist and rifling pattern available to a .224 caliber bullet can, for all intents and purposes, be found on the AR platform. Even the Ruger only made Mini-14 has gone form 1/10 to 1/7 and back to a 1/9 twist. Added by the MP
[edit] Actual effectiveness of Ballistic Fingerprinting database
As for practical appliactions, ballistic fingerprinting is quite unreliable. A survey done in California, under ideal conditions, yeilded the following:
- A recent study by the State of California points to further practical difficulties with ballistic fingerprinting. The study tested 790 pistols firing a total of 2,000 rounds. When the cartridges used with a particular gun came from the same manufacturer, computer matching failed 38 percent of the time. When the cartridges came from different manufacturers, the failure rate rose to 62 percent. And this study does not even begin to address problems caused by wear, so the real-world failure rate can be expected to be much higher.
A match in the study meant that the correct gun was in the top 15 best matches; in reality, only the top 10 matches would be considered a hit. And of course, this is a database with only 792 guns in it; if every gun were "fingerprinted", as many lawmakers want, then of course the database would contain millions (for just newly sold guns) or hundreds of millions (if all are fingerprinted) guns, making a postive ID nearly impossible.
All the guns were the same make and model--S&W 4006--used by the CHP. From personal experience with both makes, I can say that S&W uses similar barrel making techniques, and similar machine tools to machine the breech face of the slide. The S&W firing pin is machined, as it is round, the Glock's firing pin is stamped, as it has a square profile. Toolmarks should be similar on both guns. Since matches were possible, that proves that even identical makes and models using the same lots of ammuntion will generate uniquely marked cases; however, the differences between individual cases from the same gun are as wide as the differences between guns.
The only real use of the technique is as a means to assign a probability that a given cartridge case or bullet came from a given gun. scot 14:46, 6 October 2006 (UTC)
