A controversy is brewing in New Zealand about the ability of a bullet to start a fire when it strikes a rock. Below is an excerpt from an article at TVNZ.co.NZ:
Experts on fires and firearms are offering to help a Dunedin hunter fight the Otago Rural Fire Authority which is fining him over a bushfire. Tom Dodds has been accused of starting the fire, which he called in, and he’s been charged more than $60,000 by the fire authority for the cost of putting it out.
Seven Sharp reported earlier in the week that the fire investigator believes Mr Dodds’ bullet ricocheted off a rock, bounced 80 metres and hit another rock, which caused the fire 45 minutes later.
The programme reported last night it has received a lot of feedback on the case, including expert opinions from fire and firearms investigators.
One was straight to the point, calling the authority’s version of events impossible. Another, with 40 years experience, had never heard of a bullet causing a fire.
Causing a fire 45 minutes later is difficult to comprehend unless it was smoldering before it was detected.
It is a fact, however, that it is possible for a bullet striking an object to ignite a fire. We covered research on this topic in December, 2013:
…This research shows that fires can be ignited by hot fragments of the bullets due to the heat generated when the kinetic energy of the lead, copper, or steel is transformed to thermal energy by plastic deformation and fracturing from the high-strain rates during impact…
Coincidence or not, on Thursday the National Interagency Fire Center in the U.S. distributed this tweet:
If you’re heading out shooting this spring, just keep in mind that some ammunition can spark wildfires in dry grass! Be safe!!
— BLM NIFC (@BLMNIFC) March 31, 2016
In the New Zealand case, it’s probably not sparks from the rock that created a problem, but hot metal from the bullet itself that may have started the fire. It is possible that when the bullet hit the first rock, hot metal fragments were created which flew 80 meters and landed in flammable material. A second rock may not have played a significant part.