So like many on this forum , I've bought , built and sold a lot of AR's . I'm nobody special. Just someone with above average trigger time on the 5.56 . But not as much as many here. That being said, you kinda get used to what you know. You build a gun with quality parts at a cost of $1500 - 2k and you get a feeling for how it's going to shoot. After all, it's all the same shit. But then I decided to try the KAC upper route. Dropped a pinned 14.5 Mod2 on an Aero Precision Enhanced M4-E lower. F'ing-A its smooth. Follow up shots are real fast. Faster than my BCM 14.5 middy - and that's a soft shooter. So I'm finally a believer. Not going back to regular mil spec. It's worth the coin.