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| Fill 'em Full of
Tungsten
by
Jonathan Beard, New York
The following article
appeared in New Scientist on 2 December 1995, reprinted with kind permission.
Between 400 and 600 tonnes of lead are used to make bullets each day in the US, and a
high proportion of it is left to clutter up shooting ranges. Now engineers at Oak Ridge
National Laboratory have developed a lead-free bullet to tackle what has become a major
pollution headache.
The new ammunition is based on a powdered- metal composite of tungsten, tin and other
metals. It promises to be non-polluting and recyclable. The only drawback is cost: at 25
cents per bullet, it is five times as expensive as lead projectiles.
Even so, the inventors believe the bullets could save the
owners of firing ranges a lot of money because the lead problem is so big. "The
Department of Energy, which owns ORNL, expends about 10 million rounds of small-arms
ammunition each year, depositing over 300,000 pounds of lead and copper on DOE
ranges," says Rick Lowden, the engineer behind the new bullets.
"But this is small compared to civilian, police and military usage which combined,
is tens of billions of rounds per year - one estimate is that 400 to 600 tonnes of lead
are used to make bullets every day in the US." According to Lowden, it costs $65 per
cubic foot to remove contaminated soil from firing-range backstops and treat it as
hazardous waste. "At that rate, it could easily cost $100 million to clean up a
single range," he says.
The new bullets rely on tungsten to make them dense enough to perform as well as lead
bullets. The tungsten is blended with tin and other softer metals to control the bullet's
behaviour on impact. The powdered metals are pressed into cores and cold-formed into the
final bullets, using the same techniques ammunition makers now use with lead, says Lowden.
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