Updated at 6:45 p.m.: Revised to include a comment from Guinness World Records.

A West Texas man has taken aim at becoming one of the world's top marksmen.

Bill Poor, 41, says he hit a target from 3 miles away with a .408 bullet on Jan. 14 near Midland.

Hitting a target from that distance would break the record of 2.8 miles set by retired Navy SEAL Charles Melton in September.

For Poor, it was a shot that was three years in the making.

"It didn't happen overnight," he said. "It took a lot of homework and a lot of science."

His efforts have brought him attention from reporters and firearms enthusiasts, but establishing his record may prove difficult.

Guinness World Records did not recognize Melton's shot — and probably won't acknowledge Poor's either.

"They do not recognize shots with optics," said Poor, who used a large scope on his rifle. "Several guys have tried and sent them in everything, but for some reason they just don't want to take it."

A spokeswoman with Guinness World Records said that they do so to keep the playing field level, as optical devices can vary significantly.

Bill Poor and his .408-caliber rifle. (Bill Poor)

Poor used a custom-built rifle from a gunmaker that specializes in crafting firearms for extreme distances. Both he and Melton used the same base round: a .408 CheyTac, originally designed for snipers operating at long range.

While it reportedly took Melton 38 shots to hit his target, it took Poor just eight.

Poor had to account for variables that can alter a bullet's flight, including the shape of the earth. The earth curves nearly six feet over 3 miles, so he had to use an elevated stand to see his target.

"We call it dope — how much elevation you have to put in your scope to be able to see that far," Poor said. "Getting a clear view is almost impossible."

Temperatures in the mid-50s also complicated the shot. Because cold air is heavier, it causes a bullet to drop more than warm air would. To compensate, Poor aimed well above the horizon, adjusting his aim after each shot with the help of two spotters.

"It's a 14-second flight time," Poor said. "It's 10 seconds before the spotter downrange can hear the boom of the rifle going off, and another four before the bullet hits the target. You have that much time and you're thinking 'This is it.'"

But Poor's mark may not last for long, as Melton is already crafting plans to take back the record.

"Stand by," Melton said. "We are about to do 6,000 [yards]" — 3.4 miles.