If your not going to go the wssm route I suggest selling the whole rifle and starting over. Just seems more prudent than having to modify the bolt to make it take skinnier cartridges while modifying the magazine well/magazine etc to accept longer cartridges, assuming this super short action would be able to function as a repeater with anything longer than wssm s in the first place!
If you're attached to this action/rifle (and I totally understand that
) I say stick with the wssm OR more interesting and less practice, turn it into a dedicated single feed affair and chamber it for a wildcat if you handload, notably the 6 mm wsm, 6mm Saum, or as
@Andrew Massi stated, the 6mm prc.
something tells me a 69 grain absolute hammer out of a .270 wsm necked down to 6mm might occupy a truly unique performance niche.