If at all possible I always use the same hand and just replace the spring. If the gun was working fine when the spring broke then the hand is already fitted properly so I don't mess with it. I just make a new hand spring out of a bobby pin. CAREFULLY, barely flare the crimp enough to remove the spring fragment and cut a section of bobby pin to match the length of the original, bend it to shape, and re-insert it into the hand spring slot. I put a slight "waist" in the spring so when I crimp the spring in place there is some purchase to keep it from pulling out. I probably have 3 or 4 C&Bs that are running on bobby pins and so far none of them have broken. I usually use a flat head screw driver or chisel to stake the spring in place.