Erasing Ballistic Fingerprints, by Bill Twist, June 28, 2000

As a public service, this weeks column is about some practical matters, and only tangentially political. With the passage of bill S08234 in the New York Senate, and recent information about the formation of the Integrate Ballistic Imaging System (IBIS) being set up by the BATF, I thought some practical information about defeating these systems would be appropriate at this time. I would ask that you print this out and send it to your representatives, state and federal. Tack it up at the local gun shop, and give it out for free at the next gun show.

The first thing to remember is that they can't image or match what they don't have. Guns that spew spent casings, like semi-autos, leave more evidence. This can be overcome, of course, but it requires more work. Also, guns that don't leave rifling marks on the projectiles (like shotguns) can't be matched either. All of these systems work with two principles in mind: rifling leaves identifiable marks on the bullet, and the act of firing leaves identifiable marks on the cartridge case. Unless you use a smoothbore muzzleloader, there is a possibility of tracing either the bullet, the cartridge case, or both.

Let us take rifling marks first. The thing you should understand is that these marks change with wear, rendering any registration of the rifling marks eventually useless. If you want to defeat such a registration system, you must hasten the wear in the barrel. If the gun was entered into a registration system before you bought it, you have a couple of options. =0 First, if it is a semi-automatic handgun, you could simply buy another barrel. Barrels are uncontrolled, and easily swapped in and out of semi-autos. If you don't want to go to the trouble (or possible paper trail) of buying a new barrel, or if you can't easily change the barrel in your gun, you must change the marks the rifling makes.

You can't change the rifling itself, unless you re-bore the barrel. But you can change the microscopic characteristics of your particular gun. This can be accomplished by soaking a patch in an abrasive and running it up and down the barrel vigorously several times. You can also "fire-lap" the barrel, which is more involved, but just as effective (and more conducive to accuracy). Both of these methods will change the particular "fingerprint" of your barrel. If and when a bullet fired from your barrel is scanned, it will not match any previous sample from your barrel. The most that could be said at that point is that the two samples (one from before you performed the operation, one from after) came from the same caliber and type of gun, but that the two samples don't match.

The other thing you have to worry about is spent cartridge cases. Spent cases are ejected forcefully from semi-automatic firearms, less so from manually operated arms like bolt, lever, and pump actions, and they aren't ejected at all from revolvers. Since we don't have to worry about revolvers, this mostly applies to other firearms (including rifles and shotguns). The firing pin, ejector, extractor, breech face, and chamber all leave unique marks on ammunition cases. All of those parts can be replaced to one degree or another, or modified to change their characteristic tool marks and imperfections.

With firing pins, extractors, and ejectors, the simplest method is to simply buy new ones and