FYI that hammer mainspring has to be hand fit for length so it trips your ejector mechanism for that barrel properly. Too long and the ejector won't work.
Okay, let's talk about fitting the spring for proper working of the ejectors.
I reassembled the shotgun today with the new ejector hammer. I did NOT install a new mainspring as I never ordered one.
Some good luck, as both ejectors now work and are well timed.
The problem is that the right barrel will trip without firing the gun as you open the barrels to their FULL OPEN position. That final, tiny bit when you have to push the gun open against spring pressure. As you can see in the pic, the mainsprings extend quite differently from the frame.
I have some ideas about this, but will just ask: What do I need to do to keep the right ejector from tripping unless the barrel has been fired?
What I have tried to show is the following:
1) Right mainspring extends much further from the frame.
2) Right ejector trip in forend sits much deeper into forend iron.
EDIT TO ADD:
I am impatient and so moved forward.
Using marking compound, I started removing material from the longer mainspring. I had to remove enough that it is just a tiny bit longer than the left.
It is now my opinion that someone had attempted to repair this shotgun in the past. The gun had clearly been apart before. It would appear they ordered a new mainspring, but not the ejector hammer.
Gun now functions properly, with well timed ejectors!