Killing a bull elk with a 6mm has been done time and time again. My experience has been with 308 Win, 338 Win Mag and 444 Marlin. With shoulder shots, the last two put down elk much better than the 308 Win ever did. I never shoot elk in the lungs if I can help it, I always drill the shoulders to shut them down (the 338 Win Mag is exceptional in providing quick kills and no tracking). The 6.5mm chamber is fine, a shoulder or lung shot made well and you'll harvest the animal. Like all shots made on game some are better than others. Big animals can sometimes travel long distances regardless of caliber, an elk hit with a thirty-five bore will bleed like a stuck pig, hit with a 6mm-7mm, not so much. That's the only difference, and when tracking it can make all the difference. There will always be a noticeable difference in hitting a bull elk or any 600+ lbs game animal with a medium bore (.338, .358, .366 or .375) vs. a small bore for if there wasn't there would be a need for medium and large bore cartridges in the first place. Shoot well.
