(Editor's Note: This is part three of a four-part series on the U.S. Army Sniper School at Fort Benning, Georgia. For previous installments in this series, please see the links at the end of the article.)

FORT BENNING, Ga. -- For candidates at the U.S. Army Sniper School at Fort Benning, Georgia, their first three weeks at the school tested their physical limits as they crawled through mud trenches in ghillie suits and patiently crouching in marshy, bug-infested terrain for hours, practicing target detection and reconnaissance.

By week four, the remaining students had surmounted the most physically difficult portion of the school, but the course's mental trials were just beginning.

WEEK FOUR: MARKSMANSHIP BASICS/NIGHT FIRE

In week four, students were taken to a range and practiced firing the M110 Semi-Automatic Sniper System throughout the day. In the evening, they practiced night fire. This training enabled students to use their rifle scope in limited-visibility scenarios.

Most nights, students fired about 60-80 rounds. The targets were a little bit closer, between 300 meters and 600 meters. Old ammunition cans were hung on the back of the targets filled with charcoal, simulating human body heat, so that when they were hit, targets would heat up and be easier to see in a student's thermal sights. This went on for the first four days of the week.

Later in the week, students practiced to qualify in night unknown distance fire. Friday was unknown distance record fire.

The students were later called up to the line in sniper shooter/spotter teams. Two groups of instructors graded the hits/misses. The students were given a set of five targets and a time limit. They had to locate, determine the range and engage their set of five targets in seven minutes or less. They had two rounds per target to score points. A first-round hit was worth 10 points and a second-round hit worth five points.

If the student hit the target with the first round, he could move on to the next target. Once the first student engaged all of his targets or his time had expired, the sniper team moved to the next group of instructors and switched positions. The team had to score a collective 70 points to pass this record fire.

This was nerve-racking for some students who couldn't make quick shot corrections. If one team member was not on his game, then both students could fail this event and be disqualified.

Three students failed record fire and were sent home.

WEEK FIVE: UNKNOWN-DISTANCE FIRING, MOVING TARGETS

Week five was devoted to training students in unknown-distance firing and moving targets. At the range, students learned that most targets are not stationary, and they learned how to lead a moving target.

Students meticulously calculated distance range, and learned how to engage moving targets using different techniques from 300 to 600 meters. Targets moved at a slow walking pace, and were 10 inches wide to simulate a Soldier walking on patrol.

"In an operational environment, most targets will never be stationary for an extended period," said Staff Sgt. Brian Moran, one of the 11 instructors at the school. "Students must learn how to properly lead their target so the round will impact a given position when the target will be there."

In this training, some of the students were stationed behind large concrete berms. They held 10-foot tall sticks with targets at the top. The students in the pits walked the targets back and forth as other students on the line fired. A sniper instructor in the pits called cadence to keep students with the targets walking at the same pace.

After about two hours the students switched positions so that everyone could fire. After dinner, they waited for night and went back out on the range. During the night, students placed chemical lights on the targets so they could see better, firing from 300-600 yards.

Two students failed record fire.

TEAMWORK: SHOOTERS/SPOTTERS

During weeks three through five, students train together in teams of two, alternating as spotter and shooter. The spotter does most of the calculations, judges the wind, and provides the necessary data to ensure the shooter hits the target, Moran said.

"Shooters and spotters are trained to work in tandem, in two-man teams, to take out enemy targets with one accurate shot," he said.

Moran said the spotter uses a hand-held ballistic computer called an Advanced Ballistic Calculator and a book that contains data of previous engagements.

The distance of each target requires an elevation dialed onto the scope. The ABC takes in the muzzle velocity, atmospheric conditions, and the caliber of the weapon to provide the elevation. The data is recorded in the data book.

A spotter carefully uses a high-powered optic to read the wind's speed and direction. Always vigilant, the spotter also protects the shooter with his M4 rifle. To graduate, students need to be proficient both as a sniper and as a spotter and have to pass as a team.