A 300 win mag has right at 1000 ft/lbs energy at 900 yards with a hornady factory 180 BTSP. More than plenty for a white tail. That is with a 24 inch barrel. Assuming 3100 FPS MV. Used to be the heavy mag stuff, now I believe they are achieving the same with superformance. But you said you do not have as much energy as a 30-30, that doesn't make sense. Elk have been killed with the 30-30 for years until someone came along and told the hunters doing it that it wouldn't work anymore and they needed a 30-06 then 300 win mag then RUMs. No not at long range, but at 100+, and that bullet is only carrying about 800 ft/lbs at 100 yards. You got that at 1000. But true, not the velocity for expansion. Either way there are better bullets out there that will hold out that far.