S&W 642 Mainspring Tension

Question
I live in Washington State.  My wife recently purchased a S&W 642 Airweight .38 +P; this is the one with the internal hammer.  She loves the weapon except for the tension on the trigger.  She cannot squeeze the trigger more than a couple times, and even then she's straining so badly that she has difficulty hitting the target.  My question is:  Is it possible, and of course safe, to replace the main spring to reduce the tension on the trigger?  Is there another way to reduce the tension on the trigger?

Thanks

Answer
It is possible, but I would with qualifications not recommend it if this is a self-defense gun.

This is not because the trigger will be too light. People can be trained to not fire prematurely on guns with triggers as light as 4 lbs. It is because the hammer strike will be too light. The engineers at Smith have determined the hammer weight to insure ignition of the primer. By lightening the hammer spring you compromise the gun's ability to fire every time.

The factory hammer spring is rated at 8.5 lbs. Wolff Springs (www.gunsprings.com) offers an 8 lbs reduced power hammer spring (these are the spring weights, not the trigger pull weights). Wolff does not offer a lighter spring than this, and I would never recommend going lower. Even at that, once installed I would shoot not less than 500 failure free rounds through it before I trusted my life to it.

UNDER NO CIRCUMSTANCES should you ever clip coils off a spring to lighten it. Not only the weight, but also the length of a spring is critical to its proper function.

The other spring that affects trigger weight is the Rebound or Trigger Return Spring. Factory spec on this is 18 lbs. Wolff sells quite a variety of weights for these, but I am less enthusiastic about replacing these. It is possible to make the trigger so light that it is "short stroked," that is, it will not reset for the next shot. The spring's tendency to causes this would not be noticed in leisurely day at the range, but would become apparent when trying to shoot multiple rapid shots as one would to save her life. Though Wolff offers springs for these down to about 11 lbs, I would not try lower than 16 lbs. Even then, If I installed one I would start with the strong assumption that "this probably won't work" until the gun proved otherwise.

Spring weights are only part of the equation. Friction between parts is the other. If she really loves the gun, I would call the S&W Custom Shop and explain the problem to them, and send it to them to work on. They will know what parts to polish and perhaps recut to reduce friction, and if they replace springs, they will know the parameters for spring weights to lighten the trigger pull but still ensure absolute reliability.