A good rule of thumb with game shot, here I'd say #5s, is 35 meters, or max 40 yards, agree it does not depend on guage, you just get more shot in a 12 ga shell. Beyond that will wound more than kill. Of course, you can get 'lucky' with the golden bb, but patterns are too dispersed.
But, you know with these modern slug guns, should be able to extend your range on Jacks out to 100 meters!!
jk, Waidmannsheil, Dom.