Steve: My experience has been that hard trigger pulls are due to incorrect angle(s) of sear tip and/or hammer notch. A notch that is too deep will give a long pull, not a heavy pull. David talks about "filing" the sear and notch, but if you can cut these surfaces with a steel file, you have other problems. A stone or a diamond file is what is needed to cut the hardened surfaces. The problem surface is usually the notch on the hammer or tumbler in this case being at too acute an angle, so that the sear has to actually cam the hammer back before it releases.