Bridgeport, California (CNN) -- The snipers, dug deep into their hidden positions in the snow, peer down at the valley below, searching for movement in the makeshift buildings set up.
"The open doorway ... a guy standing in the open distance five to 30 meters," one sniper comments as he stares through binoculars at the objective more than 1,000 feet below.
There won't be a shot taken though.
Perched approximately 10,000 feet up on a mountain top in the Sierra Nevada, the Marine Corps snipers are receiving elite training, learning how to shoot and kill in freezing, rugged terrain. The experience and skills will be helpful in the unforgiving mountains of Afghanistan.
The men are already qualified snipers, but in this advanced training at the Marine Mountain Warfare Training Center in Bridgeport, California, they learn to shoot at steep angles in an extreme environment.
Senior snipers are always nearby to mentor.
"How are you guys doing?" Gunnery Sgt. David Williams asks the group, crouching down at the top of their snow fort.
"Good," the snipers reply.
"How come no one's got a stove going?" Williams asks. "No one's got any empty canteens? There you go, you should be working," he pushes the men.
Getting to the encampment is a slog through deep snow. It takes 4 1/2 hours of climbing to get to the seven snipers, trekking through snow as deep as 3 feet.
The only sign of the snipers is bark-colored head caps. They moved in the night before, climbing six miles in the darkness, with only moonlight to guide their movement. It took the group less than three hours, much faster than a civilian pace, to complete the journey.
Upon reaching the summit, the group set up a security perimeter and spent four hours digging out a snow fortification.
One sniper, who only wanted to be identified as Chris, explained, "Off to my right we have our observation post where we have eyes on with a sniper and spotter down on the objective at the bottom of the valley. We have a trench set up here on my left."
Chris, who says he is living out his childhood dream of being a sniper, says operations in the frigid mountains are especially tough.
"You move in under the cover of darkness ... the temperature last night dropped down a whole lot. Probably into the high teens," he said.
"You try to keep it small. You try to stay tactical. You've got the objective about 500 meters (a third of a mile) down the slope so you have to keep in mind the sound level you're making and staying low and out of sight."
Learning how to survive in the harsh mountainous terrain is an essential part of the training.
"It gives them initially the ability to move over this type of terrain. It's not as easy as one would think. It's not Sunday playing in the yard," Williams said.
"The mountains are a pretty formidable foe," he said. "In addition to the enemy, the mountains themselves are a threat and it takes certain skills and training to move over them efficiently and be able to still perform those complicated tasks that the battalion commander assigns them with."
The snipers often supplement the gear they're issued with supplies from sporting good stores that they feel may work better in the environment.
One essential gadget the group had in the dug-out trench was a ministove.
"You have to heat up the snow to make water. It lightens up your pack. You only have to carry about 2 quarts at one time 'cause you can just refill as you go," Chris said.
Hydrating and warmth seem to be the basics for this group. Warming layers are vital.
"We bring what we want as far as comfort items go. So pack light, freeze at night," one sniper, who wished not to be identified, said.
For these Marines, the training is very real. Many are preparing to deploy to Afghanistan in the coming weeks and months.
"The mountain sniper course focuses a lot on high angle shooting and that has a lot to do with the way the current war is shaping. We are moving out of urbanized areas and moving into more mountainous terrain," Chris said.
Another sniper, who wished not to be identified, agreed with Chris on the importance of the skills learned.
"It's definitely an asset in the military, especially in an anti-terrorism role: You need more precision, you need to be like a scalpel in a way instead of just going around guns ablazing," he said.
Precision is everything for this group, whose goal is one shot, one kill.
Williams said these snipers must be able to shoot and kill from 1,000 yards away, or a distance of about 10 football fields.
"The Marine snipers' job is to basically engage targets at long range. Essentially they are the guardian angel for the battalion. They survey the battlefield, find potential threats and with approval eliminate the threats, as well as provide reconnaissance and surveillance on objectives to give accurate information back to the battalion and let them know what's out there," he said.
About 25% of the Marines who take part in the mountain sniper training fail, but those enduring the course say they draw strength from their fellow snipers and the accomplishment that comes with completion.
"It's definitely miserable but you have to roll with the punches and you enjoy it once it's done. Once you get it under your belt there's a lot of satisfaction in it," Chris said.
CNN Pentagon Correspondent Barbara Starr contributed to this report