DH,
It soulds like a missfire, plain nd simple... Not a good thing I agree, but as youy fired so many before and a number afterwards, I wouldn't get too worried about it. I know mentally its a hang up, It would be for me as well...
Have you tried buck hammers? I know they are discoed but saw a post just the other day where they where avalible.. They did nto shoot well in my 20 USH but do GREAT in my 12 and I know many here love them in 20;s...
CW