I think the difference in the 2 or between the 2 is chamber dimensions giving the #2 higher pressure only? The headspace should be the same!I'd definitely check to make sure you are matching your barrel with the correct type of bolt- there are two types with different specs. Most are type II, but occasionally you might run into a type I. Hope you were able to solve it and get to shooting- grendel is my favorite AR caliber by far!