The .338 Ruger Compact Magnum or .338 RCM is a rimless, short-length rifle cartridge based on the .375 Ruger case. It was designed by Sturm Ruger and Hornady and released in 2008 and chambered in various Ruger rifles. The goal was to create a shorter cartridge than the big .338 magnums that would fit in a more compact rifle with nearly the same performance. Similar to the design ideas for the WSM cartridge family, but somewhat narrower which will frequently allow one more cartridge in the rifle magazine than the WSM equivalent. This round is designed for hunting medium to large sized North American game.
The .338 Ruger Compact Magnum uses a unique case designed by Hornady and Ruger based on the powerful .375 Ruger cartridge. The case is of a rimless design having the base and rim diameter of .532 in (13.5 mm) which is the same diameter as the belt on belted magnum cases based on the .300 H&H Magnum and .375 H&H Magnum. This allows the cartridge to have a greater case capacity than a belted magnum case given cases of equal length. As Ruger intended the cartridge to be chambered in short length bolt-action rifles the case length was shortened to 2.10 in (53 mm) which is similar to the .308 Winchester case. Unlike 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 to adopt them to the new Ruger cartridge.
