Help with first build, parts review

[BCHunter]

Thanks again, I've added the gas tube. I'm still a bit confused on the barrel. Sounds like I need a rifle length gas system, but many barrels recommended are mid-length. What's the difference? Faxon has midlength, but Ballistic Advantage has an 18" with Rifle length. Would that be a better option?

You need to match the length of the gas tube to what the barrel is set for by the manufacturer. If the barrel is listed as rifle length you need a rifle length gas tube, mid length needs mid length tube, carbine gets carbine length tube.