Or you could just use a revolver.

I'm sure there are a variety of factors that would influence the ballistics on a weapon, the biggest is time.

If it was recovered immediately after the 'illegal' shot was fired I imagine a clean ballistic match would be straight forward.

If time had elapsed, many more rounds fired (wear), improper cleaning (wear) or tossed into an environment where the inner surfaces of the barrel corrode, it would have to impact the ballistic print.

Watching all these shows with people throwing guns away, I always wondered why they didn't just toss the barrel and then replace it?

There was a study done in South Africa on the effectiveness of ballistic fingerprinting a few years back if anybody is interested.

http://bit.ly/DEFECTIVE-SCIENCE-GS

As I recall from my college courses on such things as firearms, tool mark impressions, etc, much of the process is a process of elimination. The terms most properly applied include "consistent with" or "inconsistent with" when examining fired bullets, cartridge cases, tool marks.

Rifling in a firearm consists of spiraling grooves to engage and induce a stabilizing spin. Manufacturing techniques vary considerably in the number of grooves, width and depth, rate of twist, and how the grooves are created (i.e.: cut with tooling, broached, capacitive discharge electrical, whatever). The tooling utilized will display unique results, and the visible traces can be expected to differ from one example to the next due to wear and tear on the tool itself in use. Differing methods and tooling are used in different factories and different parts of the world.

A fired bullet displaying impressions from 5 rifling lands and grooves would be consistent with several manufacturers. Within those parameters, a bullet of a specific diameter (caliber) with impressions of specific width and depth might be consistent with the firearms produced by a specific manufacturer. Within those parameters, impressions displaying specific striations within the cut grooves or exposed lands might be consistent with certain models produced within a specific time frame.

Cartridge cases can display markings made by impression within the chamber, against the breech face, and by the firing pin (or striker mechanism). Additional potential links between recovered evidence and a suspected firearm.

The initial analysis is largely a process of elimination, resulting in identification of a specific caliber of firearm manufactured by a specific maker. Beyond that, everything relies upon having a suspected firearm to test fire using the same ammunition type so that recovered bullets and/or cases can be microscopically compared to the recovered evidence items.

The final analysis becomes a matter of comparative likelihood. As with fingerprints, there are no known duplicates in existence, but not everyone has been fingerprinted during the history of the world, and not every fingerprint record has been compared to a specific example. What are the probabilities of any two being identical?

Juries like having a high degree of certainty, and that is what prosecutors and evidence examiners attempt to provide. Conviction of a crime (in the United States) requires proof beyond reasonable doubt, and the jury must decide if any doubt is reasonable.

Over in Northern Ireland, home of almost thirty years of non-stop urban terrorism, and therefore with a thriving and successful forensic science service based at Laddas Drive in Belfast, there is a physical record kept of EVERY legal firearm sold in the Province - a fired cartridge case and bullet, just in case. This is done so that if the firearm concerned is ever stolen and used nefariously, any recovered empty case, or bullet, can be tracked down. Needless to say, such an effort is only possible due to the small numbers of guns that we are talking about - probably less than a quarter of a million all told.

quote:

Originally posted by 83v45magna:
Watching all these shows with people throwing guns away, I always wondered why they didn't just toss the barrel and then replace it?

As mentioned above, the barrel isn’t the only part that makes distinctive marks that can be linked to a specific guns. The firing pin, extractor, and breech face all can mark the fired case, and a fired case may be more easy to recover than the projectile.

The program that tacfoley described has been tried in the U.S., and was why for a time at least fired cartridge cases were supplied with new guns and were supposed to be sent to the appropriate law enforcement agency when the gun was sold. I haven’t heard much about such programs recently, and I assume they were found to be unworkable if not useless. (I should not assume that they have been discontinued everywhere; I simply don't know.)

quote:

Originally posted by 83v45magna:
Watching all these shows with people throwing guns away, I always wondered why they didn't just toss the barrel and then replace it?

Better yet, if you're planning to do something terrible, just buy the barrel in advance and toss the "burner" barrel?

Good thing there’s no such thing as abrasives or 100 grit emery cloth … erm … uh … never mind.

With any mechanical manufacturing, each device with have a unique stack up of tolerances based on all the variables that go into the manufacturing: lot of the steel used, each step wears the tool just a little bit, time of day, temperature of the room, who the operator is, etc.

I've been working in the field for a long time and I spent several years in CSI. NIBIN is a game changer. Yes, it will absolutely connect a spent cartridge casing to a particular firearm with remarkable accuracy. I would have be you money it would be a failed technology, and I would have lost money. It's practically magic.

You'd also be surprised just how many criminals hang onto weapons. I sure was.

Shoot nyclads.

.

quote:

Originally posted by slabsides45:

quote:

Originally posted by 83v45magna:
Watching all these shows with people throwing guns away, I always wondered why they didn't just toss the barrel and then replace it?

Better yet, if you're planning to do something terrible, just buy the barrel in advance and toss the "burner" barrel?

Or just use a shotgun. Finally a use for a Taurus Judge.

A revolver, a thick towel and a 13 minute local police response time. I'm good......ya know, hypothetically....academically
speaking

Not affected by lands and grooves, but one of the forensic ballistic questions that I've been curious about and pondered for years, is whether it's possible to determine if a spent casing that was fired from a gun capable of either mode was fired single action or double action?

I'm guessing not, but I'd be interested to hear any discussion on it.

In this life we are born either lands or grooves. We don’t get to choose.

quote:

Originally posted by Modern Day Savage:
Not affected by lands and grooves, but one of the forensic ballistic questions that I've been curious about and pondered for years, is whether it's possible to determine if a spent casing that was fired from a gun capable of either mode was fired single action or double action?

I'm guessing not, but I'd be interested to hear any discussion on it.

Possibly the depth of the firing pin into the primer might be indicative. It seems to me that there is a difference in the force that the hammer falls between single and double action. And maybe it's just an illusion, because the trigger pull weights are different between the two.

quote:

Originally posted by architect:
If the "science" allows "matches" of an acceptable level of accuracy, why the need for micro-engraving promoted by the anti-2A crowd? Obviously, this is another nonsensical "common sense" law designed to achieve a purpose other than what is being proposed.

I think the micro engraving idea is done to put an id mark on the casing, not the projectile.
You wouldn't have to find the actual weapon to trace it back to manufacturing records and go from there. The recovered brass at the crime scene would have some sort of coded marking.
That's the way they try to sell it to the uninformed, so bills like it can pass.
Many of these ideas are really to add to the complexity of making and selling firearms, adding to costs and regulations that impact both sellers and owners.

The Three days of the Condor is calling for their melting ice bullets back.