New guy, first Grendel build

[offensive]

Ok, I have out off the build long enough and am now coming back to it, I have acquired a AA hard use bolt and a Kies Nickel Boron carrier, I am on a search for a 18" barrel now and am trying to get one. had an interesting conversation with Black Hole Weaponry today about why I shouldn't use a Type II bolt and use a Type I, needless to say I am torn and need to really do some more research on barrel. I am going with a adjustable gas block and a rifle length gas set up, already got a BCM upper on the way. Any barrel tips would be appreciated