The colt SAA and other old revolvers' firing pin was attached to the hammer (at least most of the newer repros have updated that part for safety). That is why they used to carry them on an empty chamber, because otherwise your firing pin would just be resting on the primer and could very easily go off if bumped. If using a repro you could similarly just remove the firing pin, if using an original (just don't do that, because what I'm about to say is an affront to history, but) you could grind that pin down enough that it'd never make contact with the primer again. Shudder.