A trick that usually works on box locks is to;

1. remove the cocking levers
2. position the mainsprings forward in the slot
3 install the hammers
4. using a modified screwdriver slide the mainspring back while compressing it until it snaps into the notch on the hammer

works for me, your results may vary.

Jim A.

I learn something every day, and a lot of times it's that what I learned the day before was wrong