The RCM is reported to having a capacity halfway between the -06 and WSM, so that'd make it quite a step up from the Federal.
THis is for the 300, but the same would apply for the 338:
http://www.rifleshootermag.com/ammunition/RS_0108_01/index1.html
THis is for the 300, but the same would apply for the 338:
http://www.rifleshootermag.com/ammunition/RS_0108_01/index1.html