You have alot of choices for barrels. Saami spec'd Chamber barrels. Lilja, Jp Rifles, Krieger, Bartlien, Lothar Walther, Black Hole Weaponry(now makes a saami spec'd chamber 18" or 20"), Criterion soon, Shilen. .264LBC barrels: Odin Works, Black Hole Weaponry, Underground Tactical, Satern Machining, Stoner Midway, brownells barrel, Palmetto State I'm sure I'm forgetting a barrel.
Type 1 and Type 2 came from Satern and PTG since its easier to sharpen a Type 2 reamer. Type 1 they use a .125 recessed bolt and Type 2 .136 IMO it's best to use a .136 bolt and Saami Chamber in a AR, if your building a bolt action either chamber is fine.
18" barrel something with a WASP contour will be fine or just a little heavier profile under the handguards is great too. If you don't want to spend a ton of money BHW is about the same price as the Stoner and better quality and they can shoot great.
Precisionfirearms makes the higher end barrels to and they have guarantee accuracy for there barrels. Example the Criterion barrels that's coming out they guarantee 3/4 MOA or better.
So it's up to you, Grendel is a great cartridge for the AR 15, will take Deer, Elk, Hogs, Speed Goats and so on.
