B&C makes stocks fro both Sporter and bull barrels, you usually just have to look at teh product desciptions at midway etc to see which is which, though i think the Duramax models are all made for heavy barrels, i'm not sure.
important question though, How new is this rifle? specificly is it one of the new model guns with the center-feed magazine?
If it is you need to make DOUBLY sure that the stock you order is meant for the new models. the Center-feed guns have a different screw spacing from the ones with the old style mag.
in the following chart i think the centerfeed magazine guns are the "3rd Gen" actions mentioned
From the Sharp Shooter Supply website
Long Action: 5.062" (all years)
3rd Gen Short: 4.400" (2006 - present)
2nd Gen. Short: 4.275" (1998 - 2005)
1st Gen. Short: 4.522" (1959 - 1988)