I have Speer shot capsules in .38 Special/.357, .44 Special/.44 Magnum, and .45 Colt. I have found them very effective at reasonable ranges (20 feet or so).

I have found fine shot to be more effective (#12 is best of all but #9 works pretty well). At the close ranges involved dense patterns work better. The more shot, the better. Fine shot will give you almost twice the shot count. Actual field tests on live tissue proves this, by the way.

Dale53