Accurate and reliable - Aero Precision M4E1 Enhanced 18in .223 Wylde SS Quantum Handguard Complete Upper Receiver with Flash Hider

For mid price range uppers you cant go wrong with this.
Accurate barrel, easy shooting, light recoil with the rifle lenght gas system. SS 416. If you're able to spend a few hundred more, BCM has a great upper, similar specs, but offers SS 410 which is incredible.
If you're in California, don't waste your time or energy trying to order a complete upper from Optics or DVOR. Though it does not violate their own policy, or the Law, local or otherwise, their Risk Assessment team will cancel your order.
Basically every other site will process and send to your doorstep with zero issue.