I have a Weaver 1000 yard. It's good for about 600 on deer or coyote which is fine since I only need it to work to about 500.
Tom got a Vortex(?) that's supposed to be good to 1600. He can range a deer to maybe 750 if it's in the open w/o other objects close gaining him 150 yards on mine but at that point, there's no practical use. At that range, you really need a rest of some sort to reduce the "shake" in order to get a good reading.
I seldom range an animal anyway. I check the distance to objects and determine how far I can take a shot.