The 338 Lapua Magnum was developed in 1983 by Research Armament Co. It was based on a 416 Rigby case necked down to .338 caliber. Later Lapua and Norma have put this cartridge into production. The caliber was designed to arrive at 1000 meters with enough energy to penetrate 5 layers of military body armor and still make the kill. The effective range of this caliber is about 1 mile (1600meters) and in the right shooting conditions, it could come very close to the 2000 meter mark, provided you have the right rifle/ammo/optics/shooter/spotter combination. This caliber is designed primarily as a military extreme range anti-personnel round. There really are no Law Enforcement applications, unless you need a super penetrating round for either armored vehicles, or for barricaded suspects. There are not a lot of rifles chambered for the .338, but the list is growing with the likes of Sako, AI, and others producing .338 sniping rifles. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.