Installed the Apex spring kit. It took maybe 15 minutes. Dry firing is now smooth. Only lessened the trigger pull by a hair over 1 lb..
Before you start, be sure to drop the mag, lock back the slide and make sure the chamber is clear. /////////////////////
Proceed at your own risk...............
A Word of caution: when you remove the plate on the back of the slide, be sure to wear glasses and keep the back end of the slide pointing away from you*************** The pin that holds the extractor in place sticks out the rear of the slide and is under a good amount of tension. If you don't keep your finger there blocking it as you remove the back plate, you will launch it. Not a bad idea to do the work inside of a clear zip lock bag with openings on each end. You could also launch it into something like a rag if you don't want to use your finger. Probably the toughest part was getting the back plate reinstalled over that pin. Really have to push it in far while you slide the back plate up. Also, you should view the Apex SD spring kit installation on you tube to see how to remove and reinstall the back plate and striker spring. There is no video for the Sigma spring kit.
Good luck!
Icemn