mattri, read this!
https://www.boydsgunstocks.com/Articles.asp?ID=149

Varmint Contour: - called out as BBC on the models we offer, these are generally a heavy contoured barrel that can be put into our varmint thumbhole design stock. You cannot fit a varmint barrel into our Classic, FT or Prairie Hunter design stocks unless you are willing to give up the 'flats' or rails on the top and sides of the forend. The stock will be safe to use but cosmetically unpleasing to look at.

Bull Barrel: This barrel is usually a straight contour, usually 1" or 1.250" in diameter. Inletting of barrel channel will be needed on our BBC stocks or on our heavier forend stocks i.e. Varmint Thumbhole.