You can buy reduced power hammer springs from Wolff's
http://www.gunsprings.com
The 'factory standard' is 20 lbs. Some pistols came with a 22lb spring; yours may have that in it.
You can buy a pack of 'reduced power' hammer springs, with a 16, 17, and 18 lb. hammersprings, for $9
Try them out, be sure your S&W is 100% reliable.
I have done this to several of my semiautos, and I've NEVER had a failure to fire or 'light' primer strikes with any of them.
But you do have to test with a variety of ammunition; ESPECIALLY if this is going to be a CC or HD pistol.
CCI primers are known for being somewhat 'harder' than, say, Federal, Winchester, or Remington primers.
Good luck.
My 5906 has by FAR the best DA trigger on any pistol I've ever owned or fired. This includes the Sigs and HK's: much more expensive pistols.