between shotguns and rifles they would be figured exactly the same except the velocity of the escaping powder in a shotgun should be quite a bit less than in a rifle. rifles are usually taken to be 4700fps for the powder but this is a working average and going from extremes like 45-70 to 378 wby they'll be way off to either side of that.
for shotshells, the weight of the powder charge is so small compared to the weight (well, mass actually) of the shot that the velocity of the powder is of little significance. not like in the case of say a 416 rigby where the powder charge is 1/4 that of the projectile.
i looked on champlins site and he's got 470 class dr's ranging from a few oz over 10# to right at 12# which will change the recoil quite a bit but as a rough #, a 3" magnum 12 of that weight will be around 30ftlbs. an 11# 470 class rifle will be abt 70. these #'s can vary widely depending on load used and gun weight. rough #, figure 2.5x the 3" mag 12.
roger
