300 wsm would be a simple fix. All you would have to do is run the reamer in your old chamber and headspace. Sizing down wsm brass to saum would cause some issues with the thicker brass being formed into the saum neck and would require some turning. I tried wsm brass for my 6.5 ss, and it wasn't practical although you would not be pushing the shoulder back nearly that far. I have not had a lot of trouble lately getting good Norma saum brass but don't know what the future will hold? The only other solution (option) would be to buy a new bolt from PTG, or the like, since every other chambering option would be a smaller bolt face.....Rich