Here is some info on the .50 cal and Effective Range:
"Range: Sniper rifles can be used with great accuracy against targets at much longer distances than ordinary hunting or sporting rifles. The longest confirmed sniper kill of the Gulf War was reported to have been made by a Barrett Model 82A1 sniper rifle at a range of 1,800 meters?nearly 2,000 yards, or almost 10 times a deer hunter's maximum effective range. Numerous engagements with large, 50 caliber guns during the war took place at 1,600 meters (about 1,750 yards). From the West Front of the U.S. Capitol, this range would allow accurate firing as far as the Smithsonian Metro station on the Mall. "
From
Gulf War
The Longest Confirmed Kill ( using a modified M2 Browning ) was during the Vietnam War by US Marine Gunnery Sergeant Carlos N. Hathcock
"Hathcock's 2500 yard confirmed kill with a .50 caliber Browning -longest sniper kill ever documented."
1 Mile = 1,760 Yards Carlos Hathcock?s longest confirmed kill: 2,500 yards.
1 Mile = 1,609.344 Meters The longest rifle shot ever recorded in South Viet Nam was in 1967. The weapon was the Remington Model 700 w/Redfield 3x9 scope. The distance was 1900 meters, distance and KIA was confirmed by a Marine 1st Lieutenant 1/5. Who was the shooter? L/Cpl. Martin E. Berry, 5th Marine Scout Sniper Platoon.