(Gun) Smoke and mirrors
Posted: Mon May 07, 2012 12:55 pm
Posted in Political Issues because I can envision DiFi and Chucky Schumer insisting that their states and the US develop a "Gunshot Residue Repository" so that crime guns can be immediately identified and traced, etc, etc, etc.
The latest issue of "Science News" (for May 5, 2012) includes an article about researchers developing a means for detecting the caliber of a gun from gunshot residue.
http://www.sciencenews.org/view/generic ... s_firearms_" onclick="window.open(this.href);return false;
My answer below was written and sent before I discovered that the online version of the article was a little more comprehensive, but not much.
RE: Smoking out clues
It’s not too much of a surprise that the researchers were able to distinguish between powder residues, they are, after all, chemically different as long as a different powder was used, but it’s a stretch to expect a particular residue to be the signature of a .38-caliber revolver and another to be the signature of a “9mm.” The problem is not enough data and too many variables, not enough guns and too many powders.
Strictly speaking, the “caliber” of a gun is merely its bore diameter, what seems to be being identified here is the designation of the cartridge, after all once again strictly speaking, both a “9mm” and a “.38-caliber” fire a projectile that is 9mm in diameter. There is even a revolver on the market which can fire both, or either, and several others without any modifications.
A: There are lots of different gunpowder formulations, and it is possible, even probable up to surety, that what one ammunition manufacturer uses for one cartridge combination, may be used by another for a different one, and that is not even considering the number of custom ammo makers and handloaders in the world. Gun powders are formulated to provide a specific impulse of energy through production of gas during a short duration burn, and a powder that works great in a 4 inch barrel just may not cut the mustard in a 3 inch barrel, both firing “9mm” and neither of the powders that work fine in those two might make a good powder for a 5 inch barrel, but one might work fine across .45 caliber, .40 caliber, 9mm and .38 caliber.
It is quite common to hear conversations, in the gun clubs of the world, about the advantages of using this powder as opposed to that powder, a rifle powder in a pistol cartridge, or a shotgun powder in a revolver in order, for example, to achieve better accuracy with less recoil, or faster cycling of a slide.
B: And then there is the question of which “9mm,” or which “.38-caliber,” we are talking about. In “9mm” alone there are no less than 16 different cartridges designated “9mm” (allowing for overlap) with the most common being the 9mm Parabellum, which I would speculate was the “9mm” in the article and some of those are also named “.38-caliber.” And .38-caliber (which in most cases is ALSO 9mm) also refers to another 9 plus cartridges, with the attendant cross pollination in naming.
And different bullet weights within specific calibers and/or cartridges sometimes require different powders in order to function well, even though they are all “9mm” or “.38-caliber” or “.45ACP” and so on.
In conclusion, in order for this process to be even close to valid, there would have to be a database of the signatures of each type of powder for every type of gun it could be used in, and which bullet weight, and barrel length, etc, a massive undertaking of questionable utility. In other words, unlike the CSI TV shows, there won’t be a magic scope that identifies the make and model of gun used just by examining the powder residue, it’s doubtful that even the caliber, much less the cartridge designation, would be strictly identifiable. While it may be possible to identify which powder residue was contributed by a particular gun, having both in hand, due to the factors mentioned above, and others, it is unlikely that just the residue will identify a particular caliber, even less so a particular gun.
Jim Longley
The latest issue of "Science News" (for May 5, 2012) includes an article about researchers developing a means for detecting the caliber of a gun from gunshot residue.
http://www.sciencenews.org/view/generic ... s_firearms_" onclick="window.open(this.href);return false;
My answer below was written and sent before I discovered that the online version of the article was a little more comprehensive, but not much.
RE: Smoking out clues
It’s not too much of a surprise that the researchers were able to distinguish between powder residues, they are, after all, chemically different as long as a different powder was used, but it’s a stretch to expect a particular residue to be the signature of a .38-caliber revolver and another to be the signature of a “9mm.” The problem is not enough data and too many variables, not enough guns and too many powders.
Strictly speaking, the “caliber” of a gun is merely its bore diameter, what seems to be being identified here is the designation of the cartridge, after all once again strictly speaking, both a “9mm” and a “.38-caliber” fire a projectile that is 9mm in diameter. There is even a revolver on the market which can fire both, or either, and several others without any modifications.
A: There are lots of different gunpowder formulations, and it is possible, even probable up to surety, that what one ammunition manufacturer uses for one cartridge combination, may be used by another for a different one, and that is not even considering the number of custom ammo makers and handloaders in the world. Gun powders are formulated to provide a specific impulse of energy through production of gas during a short duration burn, and a powder that works great in a 4 inch barrel just may not cut the mustard in a 3 inch barrel, both firing “9mm” and neither of the powders that work fine in those two might make a good powder for a 5 inch barrel, but one might work fine across .45 caliber, .40 caliber, 9mm and .38 caliber.
It is quite common to hear conversations, in the gun clubs of the world, about the advantages of using this powder as opposed to that powder, a rifle powder in a pistol cartridge, or a shotgun powder in a revolver in order, for example, to achieve better accuracy with less recoil, or faster cycling of a slide.
B: And then there is the question of which “9mm,” or which “.38-caliber,” we are talking about. In “9mm” alone there are no less than 16 different cartridges designated “9mm” (allowing for overlap) with the most common being the 9mm Parabellum, which I would speculate was the “9mm” in the article and some of those are also named “.38-caliber.” And .38-caliber (which in most cases is ALSO 9mm) also refers to another 9 plus cartridges, with the attendant cross pollination in naming.
And different bullet weights within specific calibers and/or cartridges sometimes require different powders in order to function well, even though they are all “9mm” or “.38-caliber” or “.45ACP” and so on.
In conclusion, in order for this process to be even close to valid, there would have to be a database of the signatures of each type of powder for every type of gun it could be used in, and which bullet weight, and barrel length, etc, a massive undertaking of questionable utility. In other words, unlike the CSI TV shows, there won’t be a magic scope that identifies the make and model of gun used just by examining the powder residue, it’s doubtful that even the caliber, much less the cartridge designation, would be strictly identifiable. While it may be possible to identify which powder residue was contributed by a particular gun, having both in hand, due to the factors mentioned above, and others, it is unlikely that just the residue will identify a particular caliber, even less so a particular gun.
Jim Longley
