We've all seen the situation on a firing line, where a fellow dumps in a powder charge, and in talking with his buddies forgets to load the patched ball, then fires it off. A hollow sound. It invariably is recongnisable due to it's VERY low pressure sound - no bang, no crack, no boom = a hollow sounding boosh or whatever = low pressure. Yes, this causes a badly fouled the bore - BUT- the intrepid man on the line has no difficulty reloading his rifle with it's 3/8" hickory rod and the tightly fitting VERY wet patched ball that cleans the bore as it is loaded - and we carry one, ribbing the individual as is invariably required.