Officers aim their submachine guns at small steel targets and fire short bursts of bullets that, on impact, disintegrate into copper-colored dust.

So-called "green ammo (search)" -- bullets made of iron, copper and other metals less toxic than lead -- has become the norm at the Federal Law Enforcement Training Center (search), essentially the nation's largest police academy.

Responsible for training the employees of 76 federal agencies, from the Secret Service (search) to the U.S. Park Service police, the center has virtually created a market for unleaded ammunition that officials say poses fewer health and environmental risks.

"This is one of the most significant advances in police training I've seen in my 20-plus-year career," said Mark Fritts, a senior firearms instructor at the center.

Made from compressed metal particles, the ammo was introduced at the center six years ago and now makes up 75 percent of the 20 million rounds fired annually at the center's campuses in Brunswick, Artesia, N.M.; Charleston, S.C.; and Cheltenham, Md.

The center, the nation's largest user of ammunition outside the military, started asking manufacturers in 1994 to develop bullets with no risk of injury to cadets from metal fragments when fired at close range.

When manufacturers began designing the bullets without lead, the environmental benefits became apparent.

"One bullet doesn't contain a lot of lead, but hundreds of thousands if not millions of bullets can be very significant," said Steve Taylor of the Military Toxics Project, an environmental group. "Lead is a heavy metal that remains in the environment for a very long time."

Next month, the center will close four outdoor ranges next month to begin a yearlong cleanup that will cost $2.8 million.

It had tested the ranges regularly for lead contamination and required workers cleaning up the dust and bullets to wear protective gear. Even the firearms instructors had to have lead levels in their blood checked annually.

The center estimates its switch to unleaded ammo has eliminated some 70,000 pounds of lead waste -- an effort recognized by the White House this month with an environmental stewardship award.

Center officials say savings in environmental cleanup and health prevention should offset the higher cost of unleaded ammo, which costs about 20 cents per round compared with 17 cents for lead bullets.

One of the center's biggest challenges was convincing other agencies that unleaded ammunition had the same performance as standard-issue, said Director Connie Patrick.

"We did blind tests where they didn't know if shooters were firing the lead or unleaded," Patrick said, "and it proved itself."

Because the unleaded bullets turn to dust on impact, they're used only in training. Since 1994, the military has been phasing in its own version of a "green bullet" made of a tungsten composite that's suitable for combat.

Remington Arms Co., a North Carolina-based manufacturer that has sold the center 16 million rounds of unleaded ammo since 2000, says the ammunition's popularity is catching on with law enforcement at the state and local levels.

"It's the wave of the future," said Remington spokesman Eddie Stevenson.