this has probably been covered before and people probably do it anyway!
got up this morning to go stalking grabbed gun then picked up the can to fit it to gun and as i went to put it on heard something rattle anyway shook the can and it rattled?? so stripped it down and found a seed of some sort in it ?? it must have got in from previous days stalking! this, if it had gone down the barrel without me noticing and a shot taken could have really ruined my day! so just a reminder/word of warning check your can before fitting and from now on i think a little rubber friend will be going over the can whilst out!