.338 Lapua Magnum

The .338 Lapua Magnum is a rimless, bottlenecked, centerfire rifle cartridge. It was developed during the 1980s as a high-powered, long-range cartridge for military snipers. It was used in the Afghanistan War and the Iraq War. As a result of this, it became more widely available. Wikipedia
 
Case length0′ 3″
Rifling twist254 mm (1-10")
Bullet diameter8.58 mm (0.338 in)
Case capacity7.40 cm3 (114.2 gr H2O)
Parent case.416 Rigby,.338/416
DistanceA British Sniper holds the longest distance confirmed kill fired from 2707 yards with a .338 Lapua Magnum rifle.