On my Pietta 1851 Navy I increased the tension of the bolt tail spring against the hammer to help prevent it from slipping off to the side of the cam and cutting it. Evidently that slowed down the hammer drop as I started to get one or two caps not going off on the first hit each cylinder. So I bent the mainspring to provide a better whack to the caps. For now that seems to be working. Only one misfire in 24 today and that was a cap that had no charge. Just waiting now to see if the mainspring will break where it was bent. Anyway a new spring is on the way.