Couldn't be happier! - Daniel Defense DDM4 300 S, URG, 10.3in, 300 AAC Blackout Complete Upper Receiver w/ Flash Hider

Replaced the flash hider with a SilencerCo ASR muzzle brake, then installed the upper onto a registered SBR lower. I ran several different types of 300 Blackout ammo through it including Winchester, Sig Sauer, Fiocchi, and PPU, and several different bullet weights from 110 grain supers to 220 grain subs. All cycled flawlessly, all locked back on the last shot, no matter whether I was shooting supers or subs, suppressed or unsuppressed. FWIW I was using a carbine spring and carbine buffer. Simply put, I could not be happier with this Daniel Defense 300 Blackout upper. Paired with a SilencerCo Omega 9K suppressor, I think I just found my new favorite firearm.