There was a piece in Handloader's Digest #11 (1987?) about making shotshells for pistols. 30-40 or 303 Brit. brass cut off to full cylinder length works in 44 mag or spl. There's room inside for a shortened .410 wad which stops leading. The 30-40 cases I cut down for this had the rims thinned & made smaller in diameter very carefully with a bench grinder as I had no lathe access at the time. Ugly but functional. Thinking maybe the primer pockets needed a little deepening love too but it was a long time ago. Cases are full cylinder length & need to be fireformed before the .410 wads will fit which leaded the bore terribly. A Lewis lead remover cleaned it right up. There is a slight bottleneck to the brass afterward. I used a pistol primer, worked up to 8 gr of Unique, #8 shot to full with a little space for the cardboard top wad, & 5 min. epoxy for the final load. The .410 wad works as the overpowder wad. An old 44 case was sacrificed as a top wad cutter. The primer pocket drilled out & the mouth sharpened with a DBT. A good whack with a medium hammer on cardboard scrap makes perfect top wads... push them out with a small screwdriver. Betting an inverted gas check with a roll crimp would work too. Good snake medicine at close range. More robust & effective than the plastic shot cups. The #8 shot penetrated a piece of aluminun roof flashing @ 10 ft. Very low pressure loads. After almost 40 yrs. the brass is still in the closet after a few reloads. But then...
A few years back I stumbled across some 445 Super Mag brass. The rim is correct & it only needed the top of the case squeezed down a bit to work well in both 44 mag & spl (not interchangably) with no trimming or firefoming. A 41 mag carbide sizer works for the bottleneck part to fit the choke of the cylinder. Much easier this way.
I think 444 brass shortened a bit will work for 45 Colt. It's too big at the base for the 44s.
RCBS used to make a shotshell forming die set that will feed & maybe function in 45ACP with shortened 308 size brass. Maybe they still do?
The late Mike Venturino wrote about making shot loads for snakes in his six guns. Best I remember he loaded them in the same cases as the calibers he was loading for. There was a picture of a shredded potato he used as a target, and it was pretty impressive.