I am trying to decide between a smith 642 and 638, and am wondering if one "hammer" setup is more reliable than the other? I am inclined to go with the 642, on the basis that no lint/coins/etc. can get into the action, but I recently got rid of a Taurus .357 b/c it was "light hammering" in double action mode about 50% of the time, but would still fire most of the time when fired in single action. (CCI blazer ammo, as opposed to its usual preference for winchester). nevertheless, it got me wondering if it would be better to go with the 638, so that I have the single action as a backup, I do not know much about the inner workings of revolvers, or any possible differences internally between the two. Anyone out there have an opinion or suggestion as to which model is the safer bet for ccw reliability when Mr. Murphy may be along for the ride?