
I picked this shotgun up for $135 while making another deal on craigslist. It's a Springfileld (Steven's) 5100 SxS 12ga with Tenite stock. I cleaned, decreased and lubed the action without disassembling.
I brought it to the TOO shoot and I had CJD3 take a look at it before I shot it. The one thing we didn't notice was that the left firing pin was stuck in the fired position. This obviously caused the gun to fire upon closing the action and I obviously got a big surprise as it sliced my fingers open. I'll mention that I had the gun pointed down range. I did it again several more times in a controlled manner and got the same result.
I talked to Ohiosam about it at camp that night and he figured it was either the hammer or the sear. I was able to get a complete 5100 "guts" package on eBay for $50. It took three tries to get the right combination of parts to make the gun work correctly. This is not the easiest gun to get back together. Slave pins are key. So basically, the left sear was not engaging the left hammer. It's all better now!
Left pin in fired position.

Hammers and Sears. Replaced left hammer kept original sears.

Worn cocking lever. Probably not an issue, but it's replaced.

Hammers cocked.

I love working on old firearms. The old school engineering amazes me.