Years ago I made up some of my own .357 shotshells. I did not really know what I was doing, but I did it anyway.
I used the powder dipper out of my LEE .357 die set ( I don't remember what grain weight it throws) and UNIQUE powder.
After sizing, and priming the cases, I put a dipper full of UNIQUE into each one. Then, for a 'wad' I just used a .22 caliber cotton cleaning patch. I then put as many pieces of shot (I don't remember the size, but they were small) on top of the patch 'wad'. to seal up the case I dribbled melted wax over the shot.
I made a hundred of these shot shells and they all fired and worked perfectly. They were great fun to shoot. Absolutely NO recoil, and very little noise. I remember they were pretty effective out to about 20 feet or so.
I know this is not specifically what you were asking, but I thought I would share it anyway. Maybe you will find it useful.
nWo FOR LIFE, Brother!
"The AK-47. It'll never jam, never break. Rugged, reliable, and so simple to operate, children could use it....and they do" Yuri Orlov. 'Lord Of War'