Ballistics tests

Factual Questions
1

I’m sure there are some firearms experts on the SDMB who can explain this. There’s been a lot of talk about having a national registry of ballistics “fingerprints” for guns; when a gun is manufactured, it would be fired and the marks from the barrel on the slug, and the firing pin on the cartridge, would be recorded in a database. Then whenever there’s a bullet recovered from a crime scene, but no gun, it could be compared to the database to see if it matches a registered weapon.

However, I’m told that this wouldn’t be effective because it’s easy to change the “fingerprint” of a firearm, by filing the rifling, or by replacing the barrel.

So my question is, if that’s the case, what about the ballistics tests that are commonly used already, when they want to match a gun to a bullet? Are we talking about the same thing, and if so, why don’t criminals routinely alter the ballistic “fingerprint” after they use a gun? If they could, but don’t because they’re lazy and stupid, that would be an argument in favor of a national database.

So, is the testing they’re talking about for a national ballistics database the same kind that’s done routinely by police and FBI, or is something different?

2

I’ve been hearing about this “ballistic fingerprinting” thing a lot lately, and it’s basically another kneejerk reaction that follows a high profile crime. What is done now, vs. what is proposed is not the same thing.

You can “fingerprint” all new guns, but what about all previously manufactured ones? Not to mention the fact that if you fingerprint a gun now, and I fire 10,000 rounds through it, it isn’t going to match up.

Filing the rifling is not a viable alternative. By doing that, all you are accomplishing is altering the lands of the barrel, not the grooves. To get into the grooves in an effective manner is something that requires some amount of gunsmith knowledge as well as special tooling, not to mention a rather high level of skill so that you do not affect the accuracy of a weapon. If you are going to use a weapon for a one time kill, then it’s pretty easy to destroy the mechanical evidence, but since I assume you are referring to the “sniper”, to re-rifle a barrel each time you shoot will reduce the weapon to near useless in a very short time. To re-barrel a rifle, put in a new firing pin, a new bolt/extractor each time you shoot, again requires not only a bit of knowledge, but also money. Barrels are not cheap, and although you don’t need a FFL to get a new barrel in most cases, there will almost certainly be a paper trail.

To cut it short, the database being proposed is different that what is done now, and will not solve much, if anything, IMO. I would go into greater detail but I don’t want to deal with mods on my ass about spreading what could be construed as being illegal/improper suggestions to possibly help someone that wishes to become a sniper and avoid tracking.

3

A national database of ballistic characteristics of new weapons would not instantly eliminate the danger of the millions of weapons already in use. Nor would it burden the law enforcement or gun manufacturing entities now doing business in the US. Neither would it represent a terrible imposition on the right of legal firearms use. None of those things change what it would do.

It would allow the beginning of a system which could provide rapid identification of many criminals, most of whom are not particularly adept or knowledgeable in erudite firearms science. It would be a tool; to identify weapon owners from the bullets fired from guns that they own. The fact that a sophisticated gun owning criminal could alter his gun after the fact does not mean that it would be the common practice of criminals to do so, nor that they would become arms experts because of it. The attempt to change the “fingerprint” of a gun itself would become evidence of premeditation in the use of a gun to commit a crime. While it is true that heavy use would alter some characteristics, it would not be impossible to develop plans by which such normal legal variances could be updated.

Those who oppose any law providing any limitation on the right to shoot what and when they wish will not accept it, but the level of intrusion here is very light, and the potential benefit to the normal citizen is potentially great. No, it is not a magic solution to gun violence. It is a tool, and one we now have the technology to implement fairly easily, in all ways other than politically.

Tris

“Reserve your right to think, for even to think wrongly is better than not to think at all.” ~ Hypatia of Alexandria ~

4

There’s a bloody great long thread about this already in Great Debates, but I’ll try and summarize:

-First, the main key here is that the marks left on a bullet and/or cartridge case are not unchanging, like human fingerprints or DNA. Barrels wear over time, or through negilgence, can become damaged (IE, rust) enough to render previous markings irrelevant.

-Second, marks on a bullet from a clean bore are not necessarily the same as those from the same gun with a dirty bore.

-Third, since most firearms these days are made on modern, highly accurate computerized milling machines, the differences between one gun and the next will be infinitesimal. A very accurate “fingerprinting” method may only, at best, tell the brand- which can largely be done now. Or it may indicate the bullet came from somewhere in a lot of 5,000 guns made in a certain time period. I very much doubt even a refined system will be able to make an accurate determination to an individual arm. We’ve been using human fingerprints for a hundred years, and the system still coughs up a sizable percentage of glitches or mismatches.

-Fourth, as mentioned, parts can be interchanged, and don’t leave a paper trail like the serial-numbered receiver does. The primary items leaving “marks” on the case are the firing pin, extractor, and ejector. These items are subject to wear in normal use, and often replaced.

-Fifth, the bullet itself doesn’t always remain intact. Hollow and softpoint ammunition is designed to deform and break up.

-Sixth, there’s roughly 180 million guns already out there, unfingerprinted. Along with that, there’s millions of new, used and surplus barrels, firing pins, extractors and other parts, also unlabelled, and with no tracking or serial numbering.

-Seventh, Maryland has “fingerprinted” something like 17,000 handguns in the past two years, and that database has not solved or helped solve a single crime, according to the article I read.

-And eighth, if the gun’s stolen, as the vast majority of guns used in crimes are, the system, even if it worked 100% of the time, would be worthless. All it would do is point to the person who owned it, and from whom it was stolen. If that person reported it as stolen, then what? There’s some who say to increase penalties on owners to reduce the liklihood they will be stolen, but even then, all the system will have done is turned up an innocent person who’s only crime was being robbed. It will have done nothing to solve the shooting.