Once upon a time, I got a Rem 700 .25/06, vintage 1974, when a part of the
mfg competition was to make flawless, accurate rifles BEFORE they left the
factory. It was topped off with a Weaver K10. (I later moved to Iowa and
sold it, and have been kicking myself ever since!) It would shoot 75gr
Hornady HP's moving 3300fps @ 1/4" all day long. Strangely, the trajectory
of a 100gr Hornady SP moving 3100fps was almost identical. So it was a
simple matter to use the varmint load for prairie dogs in the summer, then
switch over to the deer round in the fall. Back in the mid to late '70's, we
didn't have all the fancy equipment we have now. Getting accurately
proficient was accomplished by busting a few hundred PD's during the
summer. Compensating for the wind became second nature to
compensating for distance. Soon, no PD within 300yds had a chance
with that rifle, and there were a few taken at 400yds. By the time deer
season arrived, no deer had a chance at even 400yds. However, there
had been a few hundred "practice" rounds taken during the summer prior
to deer season.
So......would I now feel comfortable using the .25/06 on a deer at 400
yards? NO Would I feel comfortable doing the same NEXT fall if I could
hunt PD's at varying distances and wind velocities all next summer? YES
The next best thing would be to shoot a few hundred rounds at paper
at various distances, judging those distances with your own judgment,
out to 400yds, using a bi-pod instead of a benchrest (or shooting sticks,
or whatever you plan to use). Now, are you ready for a humane deer
kill at 400 yards?