I am no expert on the subject, but since I am also having troubles with getting a 338 win mag to feed properly, I have been looking into this issue recently. What I have found, is that according to the parts list on the savage website, the magazine box is the same for the magnum cartridge as it is for the standard 30-06 rounds. It is the follower that is different for the two types or cartridges. The follower is available for purchase from the Savage online parts. I think it is around $9, plus some more for shipping. In my case, the feed lips have been tampered with, so I recently ordered a new magazine box. Waiting to get that part still. So I would say look into getting the right magazine follower, not the box. Hope this helps!