12.7X99mm caliber Rifles can fire out to a MAXIMUM range of 7,400 yards. Heck... that is well over several miles. Now... accuratly how fare can you fire a high end long range rifle? 3,000 yards seems to be the MAXIMUM EFFECTIVE accuracy / ballistics range.
This is a dumb question but you seem like you actually want to know so i'll answer it. Right now in afganistan we have confirmed kills out past 2200 meters with the .408 chevy tac. The 30-06 was used to hold the former record of 1.16 miles. And the 50 Caliber was used to set the current record of 1.6 ish miles. The current standard issue 308 will engage to 1200 yards. Hell the 223 will engage to 1000 with the right loads on the right day, but is generally limited to 550 yards or so with 68 grain projectiles.
Now, heres what you do. You go to google dot com and do a search for those calibers and read all ya can. K?