remingtonman_25_06,
Years ago, when I was a young man, Hunting Magazine writers would tell us that we needed 2000 ft-lb of energy for Elk and 1000 ft-lbs for deer. Years later it changed to 1500 ft-lbs for Elk and 1000 ft-lb for deer remained the same. Many will disagree with my personal opinion but here it goes:
Given that conditions are right and precise shot placement is not a problem, I believe that 500 ft-lb will take any deer and or antelope with not a problem. Like wise, 1000 ft-lbs is all you need for an Elk. Yes, I agree that more energy is better and preferable, but you can do with these figures. That said, your 25-06 with 100 gr. NBT at around 5000' of elevation would produce just over 500 ft-lbs at 1000 yards. The 115 gr. NAB would definitely be a better choice as you would know, much higher BC, better bullet that would hit closer to 575 ft-lb at 1000 yards, assuming 3200 f/sec MV at the given elevation. Since I know that most would disagree, I'd like to know if there is any one that would concur.