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Bird Gun Explosion

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Michael Fox, PhD.



Bird Gun Explosion

A laborer at a wine vineyard regularly used a bird gun to scare birds away from the vines. The bird gun was a small pistol that used 22-cal blanks (one at a time) to launch missiles about 200 feet into the air at which point they would explode with considerable noise. One day, when the worker fired the bird gun, the missile did not launch and the plastic handle of the gun exploded, injuring the workers hand. The accompanying photos illustrate the exploded bird gun and the workers hand. It appeared that the handle had exploded from the inside out.

Several scenarios were investigated, including the possibility that the missile exploded in the workers hand or that the missile got stuck in the gun's barrel. None of the scenarios tested could reproduce the fractured plastic handle, plus they produced other physical features not seen on the evidence gun.

It was noted that the bird gun's trigger housing had a small break that might have allowed one of the 22-cal blank caps to enter the handle. Melting patterns on the break suggested it was there before the gun exploded. It was also realized that the missiles were not self-propelled, but that the 22-cal cap provided the sole force to launch the missiles about 200 feet into the air. This suggested the 22-cal caps had sufficient energy to cause the known damage.

The realizations about the break in the trigger guard and the energy of the 22-cal cap opened the possibility that a 22-cal blank cap had fallen into the handle, got caught in the mechanical firing mechanism inside the handle, exploded and caused fractured plastic handle and the hand injuries.

Using the scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) significant residues of lead (Pb) and barium (Ba) were discovered inside the exploded plastic handle. These metals were confirmed by SEM/EDS to be contained in the solder that seals the 22-cal blank caps. The firing of exemplar 22-cal blank caps using an exemplar bird gun confirmed that the morphology of the Pb-Ba solder residue matched the morphology of the residue inside the exploded handle.

All the physical evidence pointed to the cap-in-the-handle scenario as the most likely explanation for the bird gun explosion. The case settled shortly after Dr. Fox's deposition.

Dr. Fox is an explosion expert, fire expert, and chemical expert with extensive experience in OSHA chemical regulations and chemical safety.