I just installed a JP Enterprises reduced power trigger spring kit in my AR15 9mm. My previous trigger pull was 6.75-7lbs and was gritty. While I had the trigger out I used a smooth whetstone to smooth the 2 sear engagement areas on the trigger and then placed 1500grit sandpaper on the stone to further polish it. Finished it up with a little dremel polish with red compound to make it shine like a mirror.
Pull dropped from the gritty 7ish lbs to 3.5-3.75 smooth lbs. Warnings include poor ignition of hard primers. Not a worry for me with pistol primers. I didn't take a ton of pics because of all the vids and tutorials online. I will include a vid on the trigger install which is really easy. I still need to fire it to verify safe operation and will report on that when I do. This is a really easy cheap mod.
Not my video:
https://youtu.be/IZfYKQ3-B4Q?feature=shared