I have a M98 rifle currently chambered in 6.5x55 and am wondering if the action (a large ring M98) is suitable for a Magnum conversion. I am thinking of something like the 7mmRM or likes. What would have to be done for the action to accommodate such a cartridge ?

Regards

Assuming you pick a 6.5 mag or a new barrel.

At a minimum open up the bolt face.
Likley open up the feed rails and open/lenghten the mag box or replace the bottom metal.

GBF,
The bolt face will have to be opened up to accomodate the 7mm RM. The difficult decision starts with the magazine. It can be lengthened to accomodate the round and a magnum follower installed and the feed rails modified but the best fit is to get a magazine box that is sized in length and width for that cartridge. It can be made to work with the regular one but it does not function near as well as with one of the proper width. The magazine box will cost you in the neighborhood of $350 from Ted Blackburn or Jim Wisner.

And don't forget the extractor. This is a must do and probably the most difficult to do after the rail mod, to make it work correctly.

Thanks for the responses