>>63880823
>upper receiver
Whatever. LMT stripped, B5 stripped, if you want to be fancy get a LMT monolithic upper and you won't have to worry about shit anymore. Quad preferred for style.
>rail
DD - RIS II only
KAC - URX is sometimes available from V1.
>barrel
Any CHF, DD is fine since you'll have to replace it eventually. If you get a LMT monolithic upper, remember you will have to ship your barrel to dwilson for conversion.
>BCG
Phosphate, M16. If nitride, make sure they say melonite. Titanium is fine also, but not needed. Forward assist grooves aren't needed. KAC, LMT, V7, all fine. "Enhanced" BCGs are usually good from LMT and KAC. Make sure it's staked properly if you're getting one from wherever. Probably doesn't matter in current year, but shows better QC and potentially better customer service if something goes tits up.
>charging handle
PRI gas buster if you're going short. There's another no-name shop that makes good ones, but I can't recall the name off the top of my head. Someone will link it. Otherwise, whichever, ambidextrous is fine. You'll probably change it out anyway as you figure shit out and that's not a huge sunk cost.
There's your upper and it's not cookie cutter.
