I use a 3.5-15 and a 5.5-22 NSX. They are awesome scopes that are on par with any of the S&B's that I have used. I prefer the reticles you can get with the Nightforce line and I like the ruggedness of the turrets and such.
Bashaw Sports sell them.At the SHOT show a Nightforce rep was asked what made them so good and he used one to drive a nail into a 2x4..If you want to spend a bit more check out American Optics.The "Cat"uses a few IOR scopes