The Speer shot shell capsules are a grand idea. Many years ago I bought a couple of boxes and hand loaded them with shot and fired a few at a cardboard box. Most key-holed the box. I tried more powder, changed the crimp, reread the speer manual for loading the shot shell, ect. Nothing I did seemed to work. Later I solved the problem by buying a 357 Thompson Contender barrel that was designed for the TC shot shells (screwed an adapter on the barrel). Worked fantastic.... but I was disappointed with the performance of this product and had purchased it to use in my revolver.
Lemmon from rural South Carolina.