I'm going to respectfully disagree with Steve slightly on a technical point, but I think his intention is the same as mine is. Im not familiar with the .270 weatherby, but if it's a .270 winchester....being dead on at fifty will be approximately point blank out to 250 yards.
Your scopes sight line with a fifty yard zero will cross the bullet trajectory twice, once at fifty, impact high about an inch and a half at 100, crossing it for the second time at 175 or so, and about two and a half inches low at 250. Those numbers aren't exact, but they are close.
If you are trying to remain point blank out to 300, your bullet's first cross of the sight line will be somewhere around 30-40 yards, and the second around 250. You will be pretty high, maybe five or six inches at 150 yards. So as Steve said, regardless how you sight in you won't be point blank at some point in the trajectory out to 300 yards.
A bullet drop from zero of 13 inches sounds about right. Regardless of how you figure it and sight it in, a 300 yard shot is a hell of an accomplishment and is not a shot I would take this year given my lack of range time. At the very least, you need a range with something approaching 300 yards of length to know for sure you are on point out to that distance.
Also, I've found the distance of killing shots to grow somewhat equal to the same calculus a deer's antlers grow. If it's a 120 deer at 150 yards.....damn if it isn't a 140 deer at 225 yards when the telling is done. That observation is just FWIW by the way.
[This post was last edited on 11/23/11 at 11:47 AM]