Looking at energy charts for some high. BC, 100 gr bullets, I find that the energy listed at 600 yards is less than 2/3 the minimum recommended for elk. This is with a starting velocity of 3600 fps.
Make sure you correct for elevation, given that many people hunt elk at higher places.
For example, my 6.5-300 Wby launches a factory-loaded 130gr SS at 3,416 fps. At 700 yards: (1) at sea level, it's producing 1,488 ft-lbs, but (2) at 10,000 feet (which is the lowest elevation where I hunt elk and mule deer), it's producing 1,906 ft-lbs.
As a side note, the bullet also drops 8.5" fewer inches at 10,000 feet in the sky versus at sea level at 700 yds. That's a significant factor to keep in mind IMO.
