A .357 mag single shot rifle can be used as a sort of hybrid front stuffer shotgun if you so desire. Just load the brass with powder and a wad (paper, cardboard, or whatever) to hold the powder in place, then pour some shot into the barrel and stuff a small piece of paper towel (about 1-1.5" square) on top of that to hold the shot in place.
You can also make shotshell rounds by doing the same thing, but putting the shot (I prefer shot size "BB") on top of the wad and smearing a bit of wax over the top of the case to hold the shot in the case.
I use a similar technique, but with used primers instead of lead shot for pest control rounds in case I see something other than my dogs eating their food.