Yeah, so bad news: it does not work. I only made 1 batch of these hammers, so I know they are identical, and I've been selling them for a while with no issues, then suddenly in the past month, I've had 4 people with issues. #4, I thought to ask him if his gun was new, and it was. I'm leaning towards something changed slightly in the trigger group for new guns.
I can see two ways to make it work, neither great:
1. The trigger is not going far enough forward to allow reset. Forward travel is controlled by a notch in the back of the trigger, and there is a pin (smaller than the notch) that goes through the notch, so the notch limits both forward and rearward max positions. Dunno if the notch is too small, or the pin is in the wrong location, or has casting flash, but taking some material off the top of the notch would allow the trigger to swing slightly further forward. This is probably my favorite technical solution, but I advertise these hammers as 'drop-in', so I do not like asking a customer to modify their gun so my hammer fits.
2. You can take material off the back hook of the hammer. Not a fan of this one either, because messing with the sear geometry can lead to bad consequences if it is not done correctly.
Naturally, I'll refund anyone who has issues, so no one will be out anything. I find this product especially frustrating, because Benelli has different dimensions between the metal trigger housing and the plastic, and now it looks like differences within the plastic housings.