Its plenty of gun for that range. There was a guy on youtube who shot an elk @ 650 yards with a 6.5 Creedmoor(which is the 260's ballistic twin) and the elk went right down. So with proper bullet choice and placement yes it will be plenty
I'm showing over 1600 ft. lb. Of energy at 500 yds. With my load with a Berger 140 gr. VLD. Shouldn't be a problem if you put it in the right place. Is it the best round for elk at 500 yards? No. There are lots better cartridges.