Please note, I didn't recommend altering any part of the sear engagement whatsoever. The AR is notorious for NOT being the gun to do that. As I said, even experienced triggersmiths suffer from the parts getting past the casehardening and going bad. Bill Thompson does that job, and Bill Thompson also has some of those customer supplied triggers go soft according to his customers. It's not Bill fault - he can't control the parts hardness. It's the owners fault - they are modifying the trigger, whether it's paid to be done or on their kitchen table makes no difference, 500+ rounds later it starts doubling.
Hence, the point: Overall, the shooter CAN modify the trigger, it's just that some modifications are better than others. Installing the travel adjustment screw contributes MORE that the problem plagued stoning and fitting, and an owner should - I say again - be advised to do what they know WILL work, not what they could very well screw up.
If it's a field, duty, or self defense weapon, the owner really has no valid reason to alter the trigger weight of pull until they are experienced and trained in combatives or other stress conditioning. MOST of the light target triggers installed in AR's aren't justified. It's a combat weapon, not a bench rest toy, regardless of how the owner want's to use it. Not really the optimum tool for doing exactly what a 14 pound accurized bolt action can do better. We just like to tinker with things with inherent deficiencies and make them do what others think can't be done for our own ego trip. Just exactly like cars, same testosterone challenged logic.
For those inclined to put on a sling, be advised, the Infantry School policy was to take them off in combat. Slings are a CQB, MP, street patrol accessory, not a combat warrior option in a free fire zone. It hangs up on anything sticking out, and limits using the weapon as a striking tool. You CAN'T buttstroke an opponent with a sling limiting forward motion, and the sling CAN be used against you to throw you off balance.
No accessory is foolproof, every one has a disadvantage that needs to be considered, then the utility weighed to see if what it does improve on is worth doing in the OVERALL balance of what is needed. Sling? Not so much, I'd remove it in any vehicular transport on patrol, and wouldn't use it in the field, either. I do put them on hunting rifles because I can use it walking out of the field after shooting hours. Stand hunting or stalking is much more controlled than three second rushes at combat speed in dense cover - where getting hung up would leave you exposed to enemy counterfire while you dangle like a scarecrow in the wind.
Too many accessories are range and competition oriented - not combat, and what the Army issues is all combat, not competition. If it doesn't have it on there, they might have had good reason. About all the Marines did is add the Norgon ambi release. I don't see huge paddle latch charging handles, large trigger guards, sling point plates, modular grips, mag well grips, compensators/brakes, or most of the rest of what is marketed for the AR.
If anything, take a long look at the XCR, ACR, ARX, etc and see exactly how much of that super gee whiz stuff isn't on them - and they are designed and being marketed to governments world wide as the next generation combat weapon. Gotta wonder why American shooters with no combat experience or even military service continue to get sucked in deeper with tactical accessories for a quiet sunny Sunday at the range. Their own government and it's professionally trained users avoid the stuff like the plague it is.