The FSS kit runs about $80 more than their other trigger kits. The FSS moves the trigger break just slightly forward. What the kit improves most is it eliminates most all the pre-travel/take-up. With the other kits there is about 3/8 inch trigger take up until the sear starts moving. With the FSS kit, the trigger at rest position is further back than the stock or other Apex kits starting point. The sear starts moving almost at the same time as the trigger begins to move with little to no take-up..
From sear pick-up to end of trigger movement (over travel), the length of the trigger movement is similar for all the Apex trigger kits. The FSS eliminates the first 3/8 inch of trigger movement, but once it picks up the sear, the trigger movement is the same as the other Apex kits. Follow this link to the Apex video which shows the actual FSS trigger pull at the 19 minute time frame:
http://*******/FSSKIT
I have a Shield 40 with the Apex kit. So I do have the 3/8 inch of take-up before the sear starts moving. After that I have 1/16 inch total pull and a tad over 1/16 inch reset. The FSS is not available for the Shield. If you use the Apex duty/carry springs, the trigger pull is 5 to 5.5 pounds. I used the stock Shield springs and this dropped my pull to 4.25 pounds. I swapped out the Shield trigger spring with a stock Glock trigger spring and my pull is now 3.75 pounds, just where I want it. I also added a trigger over travel stop, which eliminated most all of the over travel. This video at the 8 minute 22 second time frame shows the trigger pull with the stop:
M&P Shield Over Travel Stop - YouTube
I am sure I will get comments about that being an unsafe trigger for carry and should only be used on a range gun. Improvements to a gun, that allow you to shoot it better, makes it a better carry gun. The lighter trigger pull and trigger stop, on my Shield, helps me shoot it more consistently and have faster recovery. People should practice shooting their carry gun, so they become used to the trigger pull, recoil and recovery, and can shoot it accurately. What makes a safe carry gun is training and practice, and knowing your gun. Also if you follow proper gun safety rules, your finger should be off the trigger until you know your target and are ready to fire. The Shield has a manual safety. I carry with that safety on and practice flipping it off, with my thumb, as I draw my weapon. I also might have a better idea as to how I would react in a stress situation, as I spent many years in LE, in a high crime inner city.
I would agree that a long, heavy trigger pull is what an inexperienced shooter should have. This would also apply to those that have experience, but fail to practice often with their carry gun.
Bob