As Fred notes, it's a B&C. More accurately the US made Fibermarks are B&C, while the old Japanese ones had a McMillan stock.
The Fibermark stock currently used has aluminum just at the action screws, whereas the B&C stock you would purchase has aluminum from the handgrip to the forward swivel stud. I'm hoping that B&C comes out with retail sales of the new design stock that Weatherby is using on the "new" Mark V. I have not yet seen them for sale.
You will look a while if you want a take-off stock, as I've only ever seen a handful for sale.