As Sarg say's it is the bullet(Construction) and shot placement. I can believe some of those who claim to have hit an elk 3 times in the lung and lost it. That is if using a projectile that is too hard and pencils through. Have seen this with Sambar deer-Indian elk- 30 odd blokes and dogs looking for one shot through both lungs from 5 meters with a 30-06. 220grain pill that was too hard. Some bone and bright red bubbly blood found. Deer put up 2 hrs later and bloke didn't take a shot, never found it after that. It may have traveled several miles and died or laid in mud closed the holes and lived. They have been known to do this. I know of Sambar that have been taken with a 30-30 but it would not be my choice for Elk.