Yeah, have been thinking of building one myself but I don't go to Nevada to shoot that often so I'm still just thinking about it. The last 2 or so years I mostly shoot the 1000 yard stuff at Sac. Valley Shooting Center when I can. However, I've had my 300 WM out to 1500 yards on target in Nevada.
A good piece of glass is like a fine piece of ass. There is no known substitute known to man, and neither are cheap.