Well i think i might of just got a lemon then. i bought a sigma in .40 sw and i couldnt hit the braod side of a barn. It also didn't feel very sturdy. I sent it back to smith & wesson and they installed a new recoil spring assembly. it shot a little bit better, but i just got rid of it. I was wondering how your sigmas have worked out.
Don't let your son worry about it some day....Wolf Spring Company makes a lighter weight striker spring which will make the trigger pull on your sigma a lot easier to handle. I have two sigmas and have used their springs to make the gun more tolerable.
I have a sigma it sat in the safe for 2 plus yrs because I hated the trigger. I done a little research and modified the springs , it is much better