I don't believe the .54 caliber White Mountain Carbine Barrel will fit a .50 caliber stock. the .50, is 15/16" across the flats, and the .54, is 1" across. That is to say that the barrel channel on your .50, is too narrow. An alternitive may be to call the T/C custom shop, at Fox Ridge Outfitters, and inquire about the Fox Ridge Carbine .50 caliber barrel. I believe this will fit the White Mountain Carbine stock, and is 1 in 48" twist. It is a 21" octagonal barrel, with fiber optic sights. You could also check Ebay, for a .54, they sometimes have T/C stocks, and barrels on auction.