As far as glass don't mess around. You've already sunk four figures into the beast and are going to pay $5 and up every time you pull the trigger. I'd look at Kahr, Schmidt and Bender or Zeiss in 12-24.
Here is the problem with scoping these rifles with big buck scopes. It isn't money, it is the fact .50 BMG's tear up scopes. The reason isn't what you might think. It isn't recoil, but rather the lack of it from the way the excellent muzzle brakes work. On most every heavy recoiling hunting rifle, say a .458 Win. Mag., the recoil goes one way. Straight back into your shoulder until all of it is absorbed by the shooter.
On a .50 BMG it becomes a two stage process. That is what ruins scopes. This phenomenon is much like what air rifles do to scopes. You can put a $1,200.00 Leupold on a $50.00 Crossman from Wal-Mart and achieve much the same result. Upon firing the scope and rifle starts back. When the bullet uncovers the muzzle brake ports it begins to pull the rifle forward, much like the clamshell thrust reverser on a jet engine does after the plane touches down. Then the rifle pulls forward. You as the shooter don't feel this. You simply feel the much softer "push" it all makes happen. But the scope "feels" everything. First rear thrust, then forward. A bit like hitting a brick wall in your truck....... then getting rear ended a millisecond later. Your neck is like a wet noodle. Your scope reacts much the same way.
Check out this high speed, slo-mo video. Watch the scope base, scope and rifle. It is unbelievable how much the whole thing flexes! This is a $15,000.00 Accuracy International semi auto. No matter, Sir Issac Newton doesn't care how much you paid for your scope and mounts!
http://www.youtube.com/watch?v=s5pVya7eask&feature=channel_page