So... I was picking around my safe and picked up a single shot H&R/NEF. 12ga ultra slug hunter that I had shot a few months back... and I went to open the breech and it will not open. There is not shell inside and I dont think it was adversely treated. The thumb release/lever seems to be loose and not connecting to open the breech.

Anyone have any suggestions/experience with this? Or a way to take it apart and diagnose/fix easily?

Thanks

Can't help you with how to fix it. More than 20 years ago mine did that . Had to take it to a gunsmith to fix it. Never happened again.

Did you pull the stock off to have a look see ?

Take the forearm off (should be a screw in the middle) and then try to open it.