In all my custom builds. - RISE Armament AR-15/AR-10 RA-140 Join or Die Special-Edition Super Sporting Trigger

Ive been building AR platform for 6 years, probably 20 or so different ARs in different calibers. From mil spec, to high end. Few things make a huge difference: good trigger, good grips and making everything straight and tight. RA 140 is my go to drop-in trigger. Have one in 556 AR-15, an AR 10, 9mm PCC, 300 Blk, and a 762x39 AR. Usually find em for $100 somewhere. Anti walk pins sometimes included. Grips: DfCO kung fu, B5, magpul, or reptilia. Sooner you have that A2 gone the better you’ll shoot. Also, a sound forward muzzle device, and the SMB or Silent Capture buffer springs. Some guns look cool, some are purely function. But $150 on any of these upgrades do all that. If you have a decent barrel and BCG already, and the gunsmith who built it at manufacturing was having a decent day, you have a good weapon. Thats my recommendations on essential AR upgrades after 6 years of badass builds.