Thanks for the report DoeDumper. It's always been my practice to leave the gun(s) loaded until I take a shot, or the end of the three-month season, whichever comes first. I've never had a problem with GOEX, Pyrodex, or Triple Seven. However, my guns are always loaded on a clean dry bore - no fouling shot, no popped caps/primers.
Was your load on a clean barrel, or did you pop a cap or foul the bore before loading?