My SBR has worn many uppers over the years in both 5.56 and 6.8. I build or buy an upper then get bored after 6 months and sell it to fund another one. Next one is already on order, a 9" 300 Blackout.
My original and still most favorite AR:
And before you haters poke fun at my few extra pounds, can YOU conceal a full size AR within fat folds and creases??? I didn't think so.
Upper:
Spikes 14.5 with pinned Dynacomp
Magpul flip ups
Magpul AFG
ladder covers that came with the upper
Streamlight TLR-HPs
Trijicon ACOG TA-31 w/ RMR