I agree that its likely that the stock is too short.

IMO, a double rifle should fit like your shotgun and not your scoped bolt rifles. I prefer a 15" stock for my DR and my shotguns, 14 5/8" is just right for a scoped rifle, so, if the length of your DR stock is that of your bolt rifles, try adding about a half inch with the rubber slip on or the Galco. Different pads add differing amounts of length.

JPK