"Do all" 10.5" barrel?

[AlcoholicusMaximus]

Yes..... the holy grail of .300 whisper barrels... I want to have a 10.5" .300/221 barrel that will cycle 220gr. subsonic smk's and 180 gr. supersonic game kings in an AR15, without an adjustable gas block.
I am willing to do load development until California falls into the Ocean. Is this even feasible, Or should I wait until John perfects his Switchblock? As of right now, I am going to put a .080 gas port at the pistol position after the barrel comes back , chopped to 10.5". Just need to know If anyone is cycling the action with both sub & supersonic ammo and this barrel config. .......