I've been making shotshells for my .44 magnum pistols for about 40 years.
I make the cases from .303 Savage or British or .30-40 Krag cases. The rim diameter and thickness has to be cut down to .44 pistol specs which I do with a file and an electric drill to spin the cases. I then cut the cases just short of the length of the pistol cylinder.
I use large pistol primers, and 7 grains of Unique or 6.5 grains of Clays Universal powder. To keep the shot from contacting the rifling, l use a .410 shotshell wad that is cut 1/4" shorter. I then fill the shot cup with #8 or 9 shot, and press a paper "hole" from a large hole paper punch, over the shot and seal it with a drop of white glue.
The cases are straight tapered before being shot, and are bottlenecked after. Many years ago I bought a ".44 magnum shotshell" size die from RCBS. Luckily the first pistol that I made these shotshells for was a Ruger so my size die was made for the longer neck for the bottleneck from a Ruger cylinder. Cases shot in a S&W cylinder have a shorter neck, but cases sized in my die will fit both Ruger and S&W pistols.
These shotshells will easily kill a grouse at 5 yards, and I have fun breaking station 8 Skeet targets with them.
