I also am a Vortex guy. Only time I shot 1000 yards was with a Vortex Viper HSLR in 4-16. I now own an identical one. That scope with a 308 with a flat base was dropping around 32 moa I think at 1000. Ran out of elevation and had to hold over just a bit to be on target. So yours with a 20 moa base would have plenty of adj left for that range. When I went you could look at all the scopes around and I would say 75% if not 90% were Vortex. And these were guys that spent MONEY.