Instead, the development team at Picatinny says the green bullet is “more effective” than the lead version.

In layman’s terms, that means the bullet causes more damage to its targets, ultimately incapacitating them — and killing them — faster.

“You can’t kill someone more, but you can become more consistent at incapacitating them,” Masternak said.

When the Army’s green ammunition program began in the late 1990s, it was not designed to create better bullets, just ones that would not contaminate the service’s 3,000 domestic firing ranges.

But creating a lead-free replica of the M855 rifle round proved difficult. The most successful attempt by Picatinny Arsenal used a tungsten-nylon blend. The ammunition ultimately had to be discontinued when troops discovered it sometimes flew sideways into targets with minimal impact.

By 2003, the Army was no closer to a permanent substitute when the War on Terror expanded into Iraq.

That’s when the Army began hearing reports that the lead rifle bullet, which had been used for three decades, was also not always performing as it should. Sometimes it would go right through targets without stopping them; other times it would cause large muzzle flashes as it exited the M4 rifle, temporarily blinding soldiers as they fought.

It was at that point that the “green ammo” mission was turned on its head.

Instead of simply reworking ingredients to create an eco-friendly replica of the M855 bullet, the Army would use green ammo program funding to develop a more lethal bullet that didn’t include lead.

Dean, who declined to comment beyond what he wrote in his e-book, recalls a 2005 meeting about the M855’s shortcomings when the green ammunition program came up.

“The program leads and contractors were laying out the scope of that effort when an infantry representative spoke up and said, basically, ‘Look, we’re in the middle of a war. No one gives a shit about being environmentally friendly right now. Can’t you give us something better instead?'” Dean wrote.

The green M855A1 — or enhanced performance round — is the Army’s answer to that question.

Enhanced performance

Made of a copper slug and steel penetrator, the round contains lead only in its primer, the part of the cartridge case that ignites gunpowder. The primer burns off when the bullet is fired, and the projectile itself is lead-free.

The technical explanation for the improvements can be gruesome, but it can also mean the difference between life and death for U.S. soldiers on the battlefield.

When a bullet is fired from a gun, it’s supposed to shoot straight. If aimed at a hard target — like a car door or a barricade — an ideal bullet would continue a straight trajectory even upon impact in order to penetrate the barricade and hit whoever is hiding behind it.

Once it hits a “soft target” — the military’s euphemism for human flesh — an ideal bullet would begin to tumble in what’s known as a “yaw,” bouncing off and damaging as many organs as possible in order to incapacitate the enemy.

Picatinny studied the old M855 round extensively when the arsenal decided to reinvent it. It found that, when fired at close range, the bullet didn’t always have time to yaw when it hit a person, particularly a thinner one. Instead, it went straight through the person.

“In essence, all of the anecdotal evidence was correct — the M855 could be highly lethal or highly ineffective depending on circumstances which the user could not control,” Dean wrote.

The challenge in developing the new, more effective “green ammo” was to keep the bullet’s same target-penetrating power while making sure its trajectory would destabilize upon hitting flesh.

Distributed to troops in 2010, the M855A1 is better at both tasks.

The green bullet can penetrate a 3/8-inch-thick steel barrier at twice the distance the old lead round can, according to Picatinny. It can also penetrate concrete masonry from up to 100 meters away, something the lead bullet could not do at any range.

The more than 1.5 million green bullets fired in testing consistently hit soft targets — using gelatin as a stand-in for flesh — without creating through-and-through wounds and also penetrated Kevlar body armor fabric from more than 1,000 meters away.

“In other words, the A1 will stop the enemy quicker so he cannot fire back,” Masternak said.

The upshot

Exactly who redesigned the green bullet is in dispute. In 2011, the Department of Defense was sued by Liberty Ammunition, claiming the enhanced performance round was developed using technology patented by the Florida-based company.

U.S. Federal Court of Claims Judge Charles Lettow ruled in favor of Liberty this winter, writing that the government had infringed on a patent Liberty applied for in 2005 and received in 2010. He ordered the government to pay a $15.6 million lump payment as well as a 1.4-cent royalty on every bullet purchased until the Liberty patent expires in 2027.

The Army and Department of Justice declined to comment. In its appeal, the government argues that though Liberty met with the Army and gave it sample bullets, those samples were never tested and differed significantly from the bullet the Army says it ultimately developed with a different contractor.

Within the military, not everyone has been as enthusiastic about the M855A1 as the Army. While the Air Force and National Guard also use the bullet, the Marine Corps continues to field the old leaded M855 while developing its own lead-free alternative.

That’s mainly due to concerns about whether the new bullets do more damage than lead bullets to rifles, said Col. Michael Manning, who manages infantry weapons systems for the Marine Corps. Initial testing in 2009 found that the M855A1’s steel penetrator was “chewing up” some magazines, expediting the usual wear and tear expected in military equipment.

The Army said its tests did find that the green bullet causes a rifle to “wear differently” and that the hardened penetrator can create marks on a rifle muzzle. But the Army said that issue does not affect the M855A1’s performance. Since developing the enhanced performance round, the Army has also developed an “enhanced performance magazine” to eliminate those issues.

The Marine Corps is re-evaluating the green round, and Manning made it clear that his concerns about the Army’s green ammunition had nothing to do with its ability to hit and incapacitate a target.

“There is no question that the M855A1 does perform better than the M855,” which the Marines still use, he said. “We vehemently agree with the Army that the M855A1 is better.”

For its part, the Army has continued its quest to get the lead out. Since fielding the original green bullet, Picatinny Arsenal has developed many more types of lead-free rounds, including those used by snipers and in medium-sized machine guns.

In November 2014, the Army issued two more types of green bullets to troops. As with the M855A1, tests show each new bullet outperforming its lead predecessor.

“What we’ve done is remove the lead from production, removed the lead from the training ranges, while providing the Army with a more capable, more consistent ammunition round,” Masternak said. “The fact is that we can meet our mission needs while removing the hazardous materials the Army was built on.”