Hello Bill,
I have worked on quite a few and currently own a couple, one being a 20 bore, they are among the best production guns Beretta ever made…cherish it and don’t let just anyone open it up.
They have a trigger plate action and can be tricky to take apart…the hammers need to be cocked during disassembly or the trigger plate will not drop out, so if you accidentally trip one of the triggers while trying to dismantle it you will need to put the top tang screw back on and re-cock the action.
After that make sure the lower firing pin has free movement…some times a burr or slight mushrooming at the rear of the pin will cause intermittent misfires, also inspect the tip of the firing pin, some times they are eroded/cratered and this will cause what you described.
Feel free to reach out if you need more help…always happy to discuss a good gun.
All best,
CJ
