i had a 7.62x54R dud go off after 3.5-4 minutes. It was still in the chamber and pointed in a safe direction. Probably my faulty reload.
i had a 12 ga ejected right after the failure to fire, it dropped in knee deep water/mud and it went boom right after sinking, 2 feet away from me.
i had a 7.62x39 go "click"...4 seconds... "boom".
Point is, be carefull, better wait with the thing in the chamber and pointed in a safe direction.