I recently blew out the end of my shotgun barrel shooting some old shells that may have gotten wet. My first shot sounded strange and I missed and my follow-up second shot "Elmer Fudded" the end of my barrel. The gunsmith said the wad from the first shot probably stuck in the choke because of wet powder didn't burn well and the second shot peeled back the end of the barrel. I guess I am lucky I didn't get hurt. If the sound and recoil are strange don't shoot again until inspecting your barrel for obstruction.