Looks like a Shepherd Scopes ltd. 6-18X
You can get one of these from Cabelas that's set up for the likes of .300 win mag, etc. The trick in ordering one of these is to know your B.C and velocity. They make scopes that are ready-set for various B.C.'s and velocities for around $600.
A custom one-off can be made for your personal setup, but it'll run you about $1000. Find a bullet that your rifle likes, chronograph it to achieve an average velocity spread, then send the data in with your order. pretty slick and professional company.
I used to shoot 1000 yd competition with a couple of guys that used these.
Me, I used a Weaver fixed 12X. There's an interesting trick in using the reticle to judge range. If you use a fine crosshair, long shots using "Kentucky elevation" yields pretty good consistency. I used to bust clay pigeons out to 700 yards with this setup, Frisbees at 1000. Won't win any Bench Rest competitions, but we never used benches or bipods- field positions only. Hitting a frisbee at 1000 is good enough to put a buck in the freezer as long as you have a good broadside shot, every time. My personal longest shot at game was 725 or so. Didn't use a rangefinder, just the reticle. My math must have been good enough, begause the 190 Sierra boattail took out both shoulders and dumped him flat. Half-way to him, he tried to get up, and I dumped him again for good.
My rifle of choice is a '03A3 Springfield .30-06 with a 28" med. heavy weight Fajen barrel. Picked it up at Doug's for $375, used. Sweet shooter.
I don't hunt that way anymore though.
7 Rem. Mag is a great long range caliber as well- just consider the size of the animal you're shooting at before you pull the trigger. Make sure your cartridge generates at least two-and a half the FPE as the animal likely weighs. That's my rule of thumb for long shots.