[Hellgate]

Check to see if the spring is fully seated in it's slot. If it is up a bit the spring could rub on the back of the hammer. It should only contact the roller on the hammer. That would make it harder to cock but not necessarily increase hardness of the hammer fall.

Also screwing in the mainspring tension screw will markedly increase the hammer fall if the screw is long enough to push on the spring. The older Piettas I have had did not have a functioning tension screw so you had to narrow the mainspring to lighten it. I just "tuned" a brand new Pietta Remmie for a friend and the screw regulates the mainspring beautifully. All the way out (no spring contact) and the hammer fall is too light to be reliable.