Recently my Stoeger M3000 has been failing to fire the round in the chamber. The hammer drops, but nothing happens. I eject the shell and the primer hasn't been touched. This problem is intermittent. Usually occurring once every 25 rounds. It has always occurred on my first shot except for once when it occurred on the second. I have disassembled, cleaned, and reassembled the bolt, firing pin and trigger group. Nothing looks broken, stressed, or out of place. I've been shooting factory loads, federal field and target multi purpose load to be exact. If anyone has any knowledge on what is causing this to happen I would love to know because it has befuddled me, but I am new to shotguns. I've really gotten frustrated with this occurring during 5 stand rounds and appreciate any help and advice.