Your walnut will work fine, barrel channel sanded and bedded with epoxy.
So will a Bell & Carlson "Medalist" type stock.
You will likely want a secondary recoil lug on the barrel with walnut.
No need for that with the B&C stock having full bedding block.
B&C will handle a No. 5 Sporter.
I have sanded them out to fit No. 6 sporter from Pac-Nor,
and even cut into the aluminum endoskeleton in the forend to bed a secondary recoil lug.
Ditto a McMillan claimed to be good for up to No. 5 sporter,
I have gone even bigger-barreled with McMillan.
