In countries that have serious hunter education and exams, and that includes Sweden, the suggestion when slings ar used is for the gun to be OPEN and slung on the shoulder with the barrels pointing down.
Generally speaking slings are used where and when there is more carrying than shooting, especially when dogs are used and the hunter will have to deal with his dogs a lot, like in hare hunting. It is also easier to carry game if the gun is slung. On the continent there is a lot of walking when hunting and very little static driven shooting.
