Bad primers show up ocassionally. Thankfully not that often. I've had more show up in shotshells than anything else. The most embarassing one I had was while participating in a top end regional field trial competition. I had a box of popper loads and was to fire one at the apex of the decoy toss for each dog in the finals. The decoy was tossed and click, no bang, every eye in the arena was on me, even the dog! I called out that the shell was bad and we had a do over. As soon as the event was through seveal judges and that particular dog's owner came over to check out the "dud" shell. Just like yours, deep firing pin indentation... they each shook their heads and walked away...

It has happened to me shooting skeet, talk about being P.O.'d I was.

When was the last time you had the action apart. My 870 did the same thing and I found wear the locking lug locks into the top of the receiver, it was full of shotshell buffering, foam used in shot.

my buddy had the same thing happen a few years ago you could clearly see where the firing pin hit the primer but no bang we took the gun apart and he had a 1/4 piece of bark that got down in the right place and was not letting the firing pin make full contact with the primer

That sucks. Ive had it happen with a .22 but not sluggers.

at least you didn't forget to load your gun the final morning. first time i unloaded my gun the whole weekend was the night before and I forgot to load it in the morning. luckily nothing showed up other wise I wouldn't forgive myself.