Most 18" Faxon .308 barrels use a rifle length gas system and would require the rifle length gas tube, which would fit with your gas block. Email us at Techsales@opticsplanet.com so we can confirm the length of your gas system and gas tube compatibility.
Yes, the Aero Precision AR10/AR15 Gas Tubes will work with that upper. If your barrel has a mid length gas system you will need the mid length Aero Precision AR10/AR15 Gas Tube.
The Aero Precision rifle length gas tube is 15.125" in length.
The gas tube roll pin is 5/64×5/16
No it will not, your barrel will specify what gas tube length you will need.
The gas tube has nothing to do with the diameter of the required gas block. The gas tube ONLY relies on the length of the barrels gas system.
Yes, the roll pin is included.
This gas tube will work with any standard AR gas block including a low profile gas block.
You have to know what length gas system the barrel has, period. I have an 18" barrel with a midlength gas port so I will have to have a midlength gas tube.
No one can tell you what will work with your barrel other than the manufacturer. Either find out from them or measure.
A 10.5 inch barrel most likely needs a Carbine Length Gas Tube (https://www.opticsplanet.com/aero-precision-gas-tube-carbine-length.html). I would double check with the Manufacturer of the Barrel to ensure that the Gas System is in fact Carbine and not Pistol Length.