RockZ,

Zeroed @ 320yds, if I use 3500 fps, 5000' elev, and a sight height of 2.2" with a BC of .4 I get

100 - +2.3, 300 - +1.0, 400 - -5.9

With a BC of .8 I get...

100 - +1.9, 300 - +.08, 400 - -4.8

Change sight height to 1.8" (which my scope is with low rings) and BC of .4 I get...

100 - 2.6, 300 - +1.0, 400 - -6.0

With a BC of .8

100 - 2.2, 300 - 0.9, 400 - -4.9

Changing the sight has a fair amount of affect on close range trajectory, but overall, not real big changes in trajectroy with HUGE changes in BC at those ranges and velocity. And IMO, 3500 fps is a little on the slow side for 100 gr bullet out of a 257 Wthby Mag, but maybe that is the real velocity. A change of 50 fps changes the trajectories by 0.1"

Here are a couple of online calcs that I use

External Ballistics Calculator
JBM - Calculations - Trajectory