hello, since I am new here (please read my intro post) I may be saying something already covered. I found out by accident one day while firing a new revolver many years ago why my groups were low and scattered when I tried to fire a spent case. when I pulled the trigger the muzzle jumped down and left! I had been flinching and not known it the whole time. now I use this as a training tool for myself and others I shoot with to mix some spent cases into a cylinder at random and then rotate the cylinder and close it without looking. you will see then if you are flinching or not and learn to avoid it. on rifles and muzzle loaders and shotguns I will have another person cycle the action either with a fresh or spent case without the shooter knowing which is which. try it sometime.