Baghdad, Iraq – A small striped bird sang atop a palm tree as Spec. Crysti Cason sat beneath it wiping dust off her weapon: a .50-caliber machine gun that fires hundreds of bullets a minute. She’s like a bird, too – 5-feet-4, 120 pounds, her gun nearly as big as she is. The soft-spoken 22-year-old from southwest Chicago is determined not to lose her head in hair-trigger moments of truth. She proved steady in a tough situation last week, facing down a potential suicide bomber.

Cason finds herself back in Iraq, at a camp south of Baghdad with the Colorado-based 3rd Armored Cavalry Regiment, in part because of a movie: “G.I. Jane.”

She saw a preview of the film with friends about six years ago and went back to watch it alone. “I know it’s just Hollywood,” Cason said, but actress Demi Moore’s character, a woman making inroads toward combat, inspired her.

She joined the Army at 17 as a high school junior. Back then, as a student council member and drama club president, she’d been aiming for theater school in New York.

Her father agreed to sign a waiver.

He’d served as a “tunnel rat” in the Vietnam War, parachuting into jungles and creeping into the underground mazes where guerrilla commanders directed attacks and where reconnaissance required muddy, often bloody, hand-to-hand fighting.

He can’t bring himself to talk the horrors of what happened in those tunnels. But one day with him in Chicago, looking through a box of memorabilia including his identification tags, his daughter spotted papers – his DD214 military record.

“I said, ‘Hey, Dad, can I see this?”‘

He let her read. She began to understand a bit about his service record.

In the Army, superiors assigned her to property-book duties – accounting work. She excelled. But from her opening interview on, she pressed the question: “When am I going on a mission?”

That flummoxed superiors. “I thought, ‘There might be something wrong with this kid,”‘ said Chief Warrant Officer Michael Hayes of High Point, N.C., who was in charge of the records unit.

“We said, ‘Hold it. Let’s do the property accountability work first.”‘

Yet they couldn’t help but notice what happened when she took her mandatory target practice at Fort Carson. She knocked down targets flawlessly. Her scores ranked excellent.

And in November 2003, she volunteered to go to Iraq. She manned guns there as the regiment adapted under fire for widely varied duties. Cooks became guards. Guards went out on patrol.

When Cason returned from Iraq, she began practicing more with the .50-caliber machine guns. Now, she’s one of the few women in the Army to emerge as a top gunner.

One day, her father visited. He had caught wind through colleagues in the record-keeping section – which remains his daughter’s primary duty – that she’d been angling resolutely to work as a gunner.

Her father didn’t object, Cason said. “I think he’s proud. He said he hoped I wouldn’t have to experience something like he did and not want to talk about it.”

There are fewer than 300 women serving in the 3rd ACR. Pushing against the barriers hindering women from serving in combat positions, Cason takes some flak.

Fellow gunners sometimes kid her about how the gun is almost as big as she is.

She flips it back. “I’m like, ‘Why am I with a bigger gun than you?”‘

Mostly, fellow soldiers are proud, calling her “high-speed.” Seeing a soldier so determined “feels good to me,” said Sgt. Tracy Williams, 28, of El Paso.

A few days ago, commanders picked Cason to man the gun in a rotating turret, providing the crucial heavy firepower defense of a major convoy rolling through Iraq’s deadly “Mixing Bowl,” a high-traffic area where remote-control and suicide bombers target U.S. troops.

It was uneventful for the most part. Until one of those hair-trigger moments: A light-colored van was following the convoy too closely, with a single male driver. It fit the profile for a potential suicide bomber.

Cason rotated the turret to face him. Her sergeant barked into her radio headset: “Stop that vehicle. Do what you gotta do.”

Her moment.

She raised her hand, motioning for the van driver to slow down, back off.

She leveled the barrel. She curled her finger, poised to fire warning shots in front of his tires, as trained, if the driver didn’t slow down.

He did, and the incident ended uneventfully.

“I don’t find fame or glory in shooting or harming people, especially if they are innocent,” she said. “I was relieved.”