Bullets Pop But Don’t Fly from Ammunition Fire

The Ultramax ammunition factory fire was big news Tuesday. The threat of millions of rounds of ammunition led authorities to set up a 2,000-foot evacuation zone during the fire, and firefighters stayed a half-mile back. Yet there were “no major explosions” and nobody was hurt.

Noted outdoorsman and journalist Kevin Woster asked his Facebook friends to comment on the real danger of ammo fires. The general thrust of the discussion seems to be that open gunpowder simply burns rather than exploding and bullets detonated in a fire don’t fly far unless they are in a gun, but “better safe than sorry.”

One commenter points to this brief from Liberty Safe summarizing research by forensic pathologist Vincent Di Maio on how ammunition reacts to fire:

In his book “Gunshot Wounds” Vincent Di Maio describes various experiments where ammunition was heated in ovens. He says that .22 long rifle cartridges detonate at an average of 275F, .38 Special at 290F and 12 gauge shotgun shells at 387F. The interesting thing about these furnace experiments was that in all instances the cartridge cases ruptured, but the primers did not detonate. In fact the primers were removed from some of the ruptured cases, reloaded into other brass and fired.

When cartridges are placed in a fire he confirms that the most dangerous component of a cartridge is the brass, or fragments thereof that may cause eye injury or penetrate skin, but certainly there is no evidence that a cartridge that is not in a firearm can cause a mortal wound, either by action of the bullet or the brass/primer fragments. It is important to remember however that a chambered cartridge that detonates in a fire is just as dangerous as a cartridge that is fired under normal circumstances in a firearm.

To get a better understanding of the behaviour of free-standing ammunition in a fire, he conducted experiments with a propane torch. A total of 202 cartridges (handgun, centerfire rifle and shotgun cartridges) were used. If the heat was applied directly to the base of a shotgun shell the primer would detonate, the powder would ignite and the shell would rupture. Any pellets that emerged were traveling too slowly to be recorded on a chronograph.

In rifle and handgun cartridges where the flame was applied to the base of the cartridge the primers always detonated but the powder only ignited in half the cases and in those instances the cases did not rupture but the gas was instead vented through the primer hole.

When he heated these same handgun and rifle cartridges at the front, the powder would burn and the cases would usually rupture but with few exceptions the primers did not detonate. The velocity of expelled projectiles ranged from 58 ft/s to 123 ft/s. The only exception was the .270 cartridge where the bullet velocity was 230 ft/s. Primer velocities ranged from 180 ft/s to 830 ft/s [Liberty Safe, “What Happens to Ammunition in a Fire?” retrieved 2108.05.10].

The following video shows the less than lethal results of cooking one bullet in a pot on a camp stove:

As mentioned in this TV report on a gun collector’s noisy house fire, bullets in fire may discharge, but they won’t project:

But hey, a couple million brass-covered firecrackers blasting out their shrapnel justifies any firefighter’s decision to take a step or three back.

Ultramax has made ammo in Rapid City since 1986. The company mentions the fire on its website and says it will rebuild.