The .338 Ruger Compact Magnum or .338 RCM is a rimless, short-length rifle cartridge based on the .375 Ruger case. Sturm Ruger and Hornady jointly developed the round, which was released in 2008 and chambered in various Ruger rifles. The goal of the project was to produce a .338 caliber cartridge with magnum level performance that would fit in a compact, short action rifle. The .338 RCM is conceptually similar to the WSM cartridge family, but is somewhat smaller dimensionally. This often allows for a higher magazine capacity than the WSM equivalent. Like the .338 caliber cartridges which predated it, the round is designed for hunting medium to large sized North American game. Design & Specifications The .338 Ruger Compact Magnum is based on the .375 Ruger cartridge, which originated with Hornady and Ruger. The case is of rimless design, having a base and rim diameter of , the same diameter as the belt on belted magnum cases derived from the .300 H&H Magnum and .375 H&H Magnum. This design offers greater case capacity than a belted magnum case of equal length. As Ruger intended the cartridge to be chambered in short length bolt-action rifles, they shortened the .375 Ruger parent case to to ensure a comparable cartridge overall length to the .308 Winchester. Unlike the Winchester Short Magnum cartridges, the Ruger Compact Magnums share the same diameter from case head to body. This allowed Ruger to chamber the cartridge without extensively redesigning their M77 rifle. See also .338 Lapua Magnum .338 Marlin express .338 Federal .338 Remington Ultra Magnum .338 Winchester Magnum Table of handgun and rifle cartridges References C.I.P. TDCC (Tables of Dimensions of Cartridges and Chambers) .338 RCM External links Hornady Introduces .300 and .338 RCM (Ruger Compact Magnum) Hornady Press Release Short but Sweet RifleShooter Article 338 RCM: Big Power – Small Package Ruger's M77 Hawkeye Compact Magnum Part II: Handloading the .338 RCM Realguns.com Sturm, Ruger & Company Pistol and rifle cartridges