Re: 1000 yards?
I"ve ran a few cartridges out to 1K and I've never had to use a 20 MOA base with any of them when using any Leupold scope, from 243 w/105 amaxs on up to 338 EDGE lobbing 300g SMK's, and a few more inbetween.
I had a leupold vari x II, 6-18 on my 300 RUM with leupolds standard base/ring setup and it worked out to 1200 yards which was as far as I could shoot at the time. Zero was 200 or 300 yards most of the time. I still had a few Minutes left. With my 338 EDGE I am currently running a VX3 6.5-20x50LR, SF, 30mm with leupolds PRW base/rings which is basically there version of weaver style. With a 200y zero with the 300g SMK at 2825fps, I'm maxed out at about 1350 yards on my vx3. To shoot a mile, I"m gonna need the 20 MOA base and maybe zero at 300 yards.
With the 300 RUM being very flat shooting, and Leupold scopes having a generous amount of MOA, you dont need 20 MOA bases to reach 1K.