to give real world examples here are the drops for 2 loads I shoot a bunch
all conditions are the same, both rifles sighted in at 300

6.5 Gibbs, 140 berger, MV 3180 fps, proven BC .7
both rifles fired in a 5 mph full value wind left to right
drop at 800 yards is 95.53" (11.5 MOA) drift is 14.19" time of flight is .92 sec.
bullet retains 1419 ft./#'s of energy

7mm Allen Mag, 160 nosler accubond, MV 3550 fps, proven BC is .58
bullet retains 1757 ft./#'s of energy
drop at 800 yards is 81.49" (9.75 MOA) drift is 15.9" time of flight is .857 sec


lets sum this up
700 shots and you either setback or rebarrel the 7mm, the gibbs will last 2500 because it burns about 1/2 as much powder, the 400 fps advantage in MV the 7mm carries amounts to 6 clicks of the scope but the 6.5 drifts 2" less. so to save those 6 clicks each shot at 800 you will rebarrel the allen 3 times, burn twice the powder in the course of 2500 rounds from each rifle. and the gibbs still retains well over enough energy for a clean kill at that range. but the 7mm will get the bullet there 63 thousanths of a second sooner
RR