GK

I don't think opening up a standard M98 is too difficult for a 404J. This has been done countless times. My 404J started life as a Oberndorf Type A sporter in 10.75x68 and was opened up to the 10.75x73 (404J). Feeds like a hot knife through butter. Holds 3 in the standard magazine.

Your post almost implies the 404J is a belted case which of course it is not so maybe you are just commenting in general about belted cases. The 404J is the classic designed case for dangerous game bolt rifles, with a long neck and gentle shoulder taper to ensure smooth and positive feeding from the magazine. I would imagine it must be one of the easiest cases to get to feed correctly in a modified Mauser and the head size is only a smidgen larger than the standard magnum case head size so no problems with opening up the bolt face.

You would not be disappointed with a 404J in a standard M98. Others that post here have done this so hopefully they will help you decide.