The conversion cylinder probably has a rachet that wants a shorter hand. THey usually want a longer one, but there are tolerances in manufacturing. If you fit the hand to lock up right, it will probably need a longer one for the percussion cylinder. Either get and fit a new one for the conversion, or a new one for percussion, if you are going to use both. The other alternative is to shorten the sear nose, but then the percussion cylinder will never time up unless you have a substitute trigger, but that's easier to install than the hand.
