The shot capsules are made for the straight wall pistol cases. You seat them down inside the case and upon firing, they will only receive pressure from the bottom end where the plastic lids fits on.
In the 357 Herrett, you will have to seat them really deep in order to chamber your loaded rounds. The plastic capsule will deform and/or breakup on firing since it will be seated below the neck and have pressure from all sides. You may get the shot out the barrel, but doubtful in any reliable pattern.
Steve
