I had a 9mm version of Sigma for about a month. Shot 200 rounds with it. No problems. Great gun. That's all.
I also have a Sigma 40 for carry. My gun seems to be more accurate with 180 GR. for some reason. I also have done many things out there on the NET. Your best bet is to contact Fred Smith at LSG. 325-885-2700. LSG is a certified S&W repair center. If trigger feels gritty more than likely it's cerrations on the sear (that's why everyone starts out polishing sear assembly) let Fred know that is the problem. He will give you info for free shipping for repair. Then ask him if anything could be done for lighter trigger. He will charge $60 to clean everything up and get a pull of about 10#. My stock pull was 13.5#. It made a big differance when your shooting 200 rounds at the range. Having work done at LSG keeps your warranty intact. Doing any modification to a firearm could come back and bite you on the a$$ if gun is ever used in a shooting, justified or not.
The Sigma makes for a decent carry gun. No matter what you do to it will never be a good range gun. It is what it is. The heavy trigger will make you a better shooter. You will learn to squeeze the trigger, not pull the trigger along with gun off target (wich is usually left and low).