Melanie Plenda's reporting on Sunday's fire at the Juneau Self-Storage was interesting and entertaining, too bad it contains so many myths and falsehoods about what happens when ammunition "cooks off" in a fire.
Fire causes $1 million in damage
I suppose it isn't her fault, even some firefighters are unfamiliar with the phenomenon. To get an idea as to what really happens, one only has to look to basic chemistry, what goes into a round of ammunition, and basic physics where every action has an equal and opposite reaction.
First, a round of metallic ammunition consists of the cartridge case, the primer, the powder, and the bullet (the actual projectile, usually made of lead). When a round of modern, smokeless powder ammunition ignites outside of the barrel of a gun in a fire, most often the priming compound ignites first since it is most sensitive. The priming compound (usually lead styphnate) is the only explosive compound found in modern ammunition, and it exists in a pellet about 1/16th the size of a pea. This only serves to ignite the smokeless powder. Smokeless powder is not an explosive; it is a progressive burning propellant. This means that its burning rate is enhanced by containment. (Burning creates gas which, if contained, creates pressure, which increases the burning rate, which creates more gas, which if contained, creates pressure. This continues in a gun until the inertia of the bullet is overcome and it comes out of the gun barrel with a loud bang.) Since, in a fire, the cartridge case is not contained by the barrel of a gun, the case splits at a relatively low pressure level. Because the bullet is the heaviest part of the cartridge, it moves at a relatively low velocity, if at all. The primer cup in a centerfire cartridge is often ejected at a relatively high velocity due to its small mass. Pieces of the cartridge case can break off and be ejected. Due to their relatively low mass, however, these pieces have little ability to penetrate past a few feet. Though they might penetrate exposed skin, heavy clothing and a face mask would be sufficient to stop these metal shards at any distance past direct contact. These shards of sharp metal might imbed themselves in something nearby. If there are truly "bullets imbedded in the roofs of these buildings" either somebody shot them there out of a gun, or the roof fell on the bullets and the bullets stuck. They certainly didn't get there when the ammunition cooked off in the fire. The truly dangerous things in that fire were the propane tanks, fuel, and paint. The ammunition posed little threat, though it probably sounded impressive as it cooked off regularly as the fire progressed.
I was also disappointed that a great emphasis was put on there being "3,000 rounds of ammunition stored". 3,000 rounds of .22 rimfire ammunition in its original factory boxes would fit in a standard sized briefcase. A normal competitive smallbore shooter usually searches for a particular "lot number" of .22 ammunition that shoots well in their target gun, then proceeds to buy 5,000 to 10,000 rounds of that "lot number." That 10,000 rounds would easily fit under one chair in your dining room with space for another 10,000 rounds. For an active IPSC shooter, 3,000 rounds or centerfire handgun ammunition would barely get them through a month of practice. The number sounds impressive to non-shooters, particularly when someone is busted for jaywalking and the newspaper reports that the police found 3,000 rounds of ammunition in the person's apartment, but to a shooter, one wonders why they had so little.
Brad Flynn of Juneau is an NRA-certified firearms instructor for the U.S. Forest Service and for the Alaska concealed handgun permit. He has 35 years of experience reloading ammunition and has been a competitive shooter for more than 25 years.P>
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