Update on this - rifle is functional again! I received the Zoli springs from Italy quickly. Unfortunately they were not a simple drop in fit. I have a photo of original and new one side by side. The length of one leg vs. the other is critical!! The leg facing the front of the gun (facing the hammer) must be 3-5mm longer than the rear leg facing the butt of the gun. This allows the spring to “lay back” so there is clearance for the hammer as it cocks back. If the spring legs are too symmetrical in length the spring will actually tilt forward while the hammer archs back, hitting each other and not allowing the hammer to travel enough to engage with the sear lever below the spring.
I filed on the replacement spring aggressively, removing as much material as i could from the U portion of the rear leg of the spring (trying to make it shorter) and filing the large knob on the front of the spring down effectively making that portion of the leg longer. I also had to put a significant bend in the rear spring leg to lean the spring backward and also shorten the leg a bit. It was a very tight fit but I managed to get the spring to work reliably. Mack fired the shotgun several times and reported 100% function.
I also ordered the Ithaca 580 springs from EBay, which took over two weeks to arrive. I am not sure how they will fit, but I know they won’t be drop-in either. I would really like to fit these springs as I feel they will be the most reliable for the long term.
Given enough time I may find a drop in spring now that I know exactly the critical dimensions I am looking for. Mackey has the rifle, it is working, and it is turkey season in MS. I may not see it again to work on it.
