The absolute best in my book is the Night Force NXS scopes. I know many Army and Marine snipers, and they steered me to the Night Force. It's what they use over in the big sandbox. I use a 3.5X15X50 NXF with the NPR-1 reticle on my 338-378 Weatherby. I've killed Moose at 810 yards, one shot kill. I've taken Grizzly at 620 yards. I am now consistently hitting a gallon milk jug full of water out to 1200 yards.
There is two problems with the Night Force scopes. They are heavy, full 2 lbs, then they are spendy, $1700.00.
The second scope I would look at, it's much lighter, would be the Leupold Mark 4. Still spendy, but a lot lighter.
The third would be the Nikon Monarch, in either the 3X12X42, or the 4X16X50.
To me what ever scope you decide on, look hard at turret mounted focus. Having the focus mounted on the left side of the scope means you don't have to reach out in front of the scope to set the parallax, it can be done while looking through the scope. I no longer buy scopes that do not have that feature.
Now I will admit to putting a Cabela's 3X12X40 Big Game Tactical Scope on my H&R 30-06 Ultra Comp. The only draw back is that the turret is only calibrated to 500 yards for the 165gr bullet. I had to develop a load to match the ballistics the scope was set for. Once I got that done I am very satisfied with the results. I no longer want to shoot wolves beyond 500 yards, bullet performance just is not there for an animal that big. I specialize in Wolves with that gun. But since you are looking for 800 yards, that is not the scope for you. I also have the Cabela's Centerfire Tactical scope in 3X12X40 on a H&R Ultra .223. I already had a load worked up that matched the calibration on the scope, using the 55gr bullet. Can't remember if the scope is calibrated for 400 or 500 yards, I'm thinking it's 500. (The gun is currently in a vault in the garage blocked by the wife's SUV. Since it's 54 Below outside I'm not going to open the garage door to move the car to reach the vault.) I have used this gun/scope combination for three years, and really like it.
Good luck in your search. Rog