It works well.....but I would NOT bet my hunt on it doing 1200 yards in every situation when you really need it IMO.
If I were in your shoes it sounds like a leica 1600 or similar is what your after.
I love my weaver 3x15 edmr....but I have also read horror stories here about warranty issues being solved.
Scope for scope I would choose the weaver over the vortex..but I am concerned if and when the day comes I need service I'll wish I'd bought a vortex....tough call.