For piston ARs and AR-like rifles, I have HK416s, CAR 816s, POF P415s, MR556, LMT MRP/MLC pistons, Sig MCX (more like AR 180), Bushmaster ACR and SCAR16.
I have both CAR816A2 uppers in 14.5 and 11.5. All are more pleasant to shoot suppressed than my DI ARs. All run significantly cleaner. The HK416s are pigs. They run awesome, but are heavy. Never had a malfunction. Eats everything I put through them. That’s true with my P415s, and my MCX, and my 816s. The 816 is the evolution of the 416, 516, MCX, and developed by the same team. My 816 uppers run awesome suppressed or non-suppressed. They’re accurate, soft shooters, and light relative to the 416s. Never had a stoppage or malfunction. I like the fine tuned piston system, the adjustable gas block, the lockup on the MLOC rail system, and fine with a nitrided barrel. Doesn’t need to be chrome lined. I bought each upper for about $1k. Worth every penny.