Is it possible to rechamber a M98 300 Winchester to 300 Weatherby, it is a Shillen barrel

The re-chamber is possible, but there are extensive modifications needed to fit the longer round in the magazene. If you want a faster 30 cal, then a 300 Dakota or similar would be a better option in a std length action.

With the 300 Dakota, you will have to open up the bolt face a little as I believe it is based on the 404 Jeffery round. No mag modifications though.

Both the above replies are correct. But, in my opinion, there's not enogh to be gained from either a .300 Weatherby or a .300 dakota over the regular .300 Win. Mag. to justify the cost of the rechambering and action alterations you would have to do. I tested a .300 Dakota extensively last summer, and was not impressed. It would safely do ALMOST 3000 FPS with 200 grain bullets. I had a 24" .308 Norma on a Springfield action in the 1960's which would do almost (within 25 FPS) of this level with the same 200 grain bullets. We haven't come very far in the past 40 years!!