Gun Tools and Gauges: Digital luggage scale substitutes for a trigger gauge.
A trigger pull gauge can run from $29 to well over $50. Because I don't use them that often I could not justify spending that kind of money (use it once and it sits on the shelf ... forever). I tested this inexpensive digital scale for less than $5.00 (included shipping). They are pretty accurate (advertised to be within 1/10th lb) for my requirements. They do not have a memory so you will have to write the measurements down each time and you will have to pull slowly so you are able to read the measurements as the hammer breaks free. $6.00 delivered! A thermometer measuring the ambient temperature in the room is an added bonus (the thermometer on mine did not work too well).