I'm trying to get my budget ready for the AR I've been building. I want to settle on a barrel, but there are many types. So, there are heavy barrels, pencil barrels, contoured barrels, fluted (straight and spiral). What are the differences that make one better over another for one purpose or other? I assume that a heavy barrel, while weighing more, would be better for long range or bench rest shooting whereas a pencil barrel is lighter but probably adds to felt recoil. Please, correct me if I'm wrong about those, but what are the (dis)advantages of the others? Are there other types that I didn't mention? Thanks in advance for any help.