Hi, I got my 642 three weeks ago and so far have shot 150 rounds. Trigger pull is heavy DAO but very smooth and crisp. I also use snap caps to practice dry firing at home (done over 300 pulls so far). While practicing dry firing today, the intial trigger pull became very stiff (not as smooth as it was). I suppose with dry firing, the trigger will become smoother. Don't know what happened. Could it bcz some dirts (metal debris from shooting) got into the gun? Any maintenance or cleaning I need to do? I plan to use the gun for CCW so I don't want to do anything to comprise its reliability. FYI, I called SW customer service. They asked me to send the gun in for check up. It's a brand new revolver. I was a bit disappointed after shooting it 150 rounds. What could be the problem? Thanks for your help.