[berettafan]

as i recall powder does not necessarily have an infinite life and can even 'leak' (evidence would be a stain on the shells near the 'brass') certain chemicals. can also be caused by poor storage (excess humidity, etc).

IF you have a misfire or all of the powder isn't ignited or the powder has degraded chemically you can have an issue where the gun fires but the wad doesn't quite make it out of the bbl. this isn't always as obvious as you might think and prudence requires you check the bbl to be sure it is clear. this is easily done every time with a break action gun like your single shot (important note is that you are able to check from the REAR of the bbl!).

anyways, if the wad doesn't clear the bbl and you fail to notice it the next shot could very well split the bbl wide open.