Another good .50cal BMG site:
http://www.biggerhammer.net/
On any other rifle besides the .50, I'd say the Leupold would be the perfect scope. They don't make better glass than a Leupold.
I would be concerned about it's durability on the .50.
After my high priced Springfield disintegrated, I'm leery about any scope that I don't know to be proven to stand up to the concussion.
Springfield fixed it, but who wants to remount a new scope every hundred rounds or so?
I'm going with a Night Force 12-42x56 NXS only because it has proven that it will hold up.
At any rate, you've got a treat coming when you squeeze the trigger of that Barrett for the first time!