Long Range Rifle Competition is a very challenging and popular form of competitive shooting, not just in the United States, but across the world.
The NRA Long Range formats involve shooting at distances between 800 to 1000 yards, shot from the prone position supported by a sling.
The most well known Long Range format is known as Palma. Started over 100 years ago, the Palma course of fire (COF) involves three (3) stages of fire, 15 rounds with unlimited sighters at 800 yards, 15 rounds with 2 sighters at 900 yards, and 15 rounds with 2 sighters at 1000 yards (45 rounds total for record). There is a 22 minute time limit for each stage of fire.
Another standardized Long Range format is a LR Prone COF, which is 20 rounds for record with unlimited sighters fired at 1000 yards in a time limit of 30 minutes. Many Long Range prone matches involve shooting two or three 20-round strings (i.e. 3×1000).
To shoot in the Palma category, a Palma rifle needs to be chambered in .308 Winchester and fire a 155gr bullet.
But many competitors opt to shoot Long Range, whether it be the Palma COF or LR Prone COF, using another cartridge (such as 6.5×284 or .300 Winchester Magnum) in a bolt rifle. It is also possible to shoot Long Range with a Service Rifle (“National Match” accurized condition, of course).
The International Confederation of Fullbore Rifle Associations (ICFRA) is the governing body for international prone rifle shooting. On the ICFRA website, you can review the general international rules as well as rules for the various International tournaments.
There is an article on Accurate Shooter (6mmbr.com) outlining the basics of Palma competition: http://www.6mmbr.com/palmabasics.html