Just read an article regarding the 300 and 338 RCM cartridges--after reading the article I feel it is a much ado about nothing...they are slightly slimmer than the WSM's so one can load 4 versus 3 in the magazine--also they "claim" to get similar velocity from a 20" barrel versus the 24 " used to chrono the WSM's and RSM's...again, seems a bit redundant..IMHO....

Ripp