https://www.joeboboutfitters.com/JoeBob-s-AR15-Grip-Screw-Trigger-Adjuster-p/jb-triggeradjuster.htm
https://www.joeboboutfitters.com/JP-Enterprises-AR-15-RELIABILITY-ENHANCED-REDUCED-p/jp-jps3.5t.htm
thats the parts list you want. the JP yellow trigger spring lessens the pull weight a bit, the red hammer spring ensures reliability with hard cup nato primers. some folks bob their hammers while they're doing this mod to decrease the lock time on their setups a bit as well.
the grip screw allows you to take up most of the travel on the trigger. Joebobs' has instructions on how to make this adjustment correctly and safely on the website where they sell the grip screw.
Quote

irections for Assembly:
***BE SURE THE FIREARM IS UNLOADED BEFORE PROCEEDING***
Separate the upper receiver from the lower receiver.
Cock the hammer back and set the safety lever to safe. THE LOWER MUST BE ON "SAFE" TO ADJUST CORRECTLY.
Completely remove the set screw from the adjuster by turning the Allen Key CLOCKWISE.
Apply Blue Loctite to the set screw.
Re-Install set screw to original position with hex head.
Remove original grip screw. Make sure not to lose the safety spring & detent!
Place adjuster into grip and tighten thoroughly with a 3/16" Hex Driver
Tighten set screw using 5/64 Hex Key. Do not tighten past stopping point.
At this point the safety lever won't move or will be hard to move. Leave on safe.
Back the set screw out 1/8 turn at a time until the safety lever moves freely again.
Function test the lower checking that hammer, trigger, and safety are all functioning correctly. This is as far as you can adjust the adjuster. Let the loctite dry overnight.
These directions are intended to aid a qualified gunsmith in installation.
The lower receiver must be drilled and tapped all the way through the pistol grip or the trigger adjuster will not be able to thread in completely. Please inspect your lower receiver prior to installation to ensure safe installation.
it wont be amazing like a $200 drop in match trigger, but its the best $30 you can throw at a mil spec trigger group while still maintaining safety margin vs stoning the engagement surfaces, which is risky at best.
they only case harden those surfaces - so the hardened engagement surfaces is only a couple thousandths thick. super easy to remove the hardened surface with a stone/sandpaper trying to smooth it out and now you have a trigger that after an undetermined amount of usage can start to run away on you (doubles, triples, mag dump, etc). Not only is that a safety issue, but it would put you in legal spot - since you'd technically be in posession/manufacture of an unlicensed MG when it does fail on you due to your modifications.
basically stick to changing the springs and the grip screw and you're in the good
you may or may not need a tap to thread the grip screw hole in your lower all the way thru. some mfg's thread the whole thing, others dont. iIrc its a 1/4-28 tap. which unfortunately Joebobs doesnt carry (that i can see) so you'll need to source one from midway or amazon if you dont have it in your tool kit already.
hth