The only dammage I have seen was from placing the brass backstrap against the bench and applying gorilla pressure. Ususally Bubba will show you his prize brass frame .44 Navy with a bent grip and exclaim "Look at that! I load it so hot it bent the grip. Hold my brew and I'll show ya!" I have heard where the teeth on the rammer and the holes in the barrel with the creeping lever (61 Navy & 60 Army) have been badly worn from extensive use and/or excessive force. I usually load with a press because it's easier and may save wear and tear on the gun but those 2 reasons are quite a way down the list. All that said forcing grossly oversize balls or ones made from wheel weights into the chambers using the lever ought to be avoided.