The biggest thing to help with your desired performance IMO would be as previously mentioned is a pistol length gas system, which most are, an adjustable gas block, and potentially increasing the diameter of the gas journal on the barrel. Many barrel manufacturers do increase them as needed but some still drill them out to the standard 5.56 diameter which can cause reliability issues with subsonic ammo. I personally would piece it together. Get what you want and nothing more or less.

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