I'm not sure. I've shot truckloads of deer and antelope using Nosler Ballistic Tips and Accubonds with much better/quicker kills at a wide variety of ranges. I haven't shot anything other than that deer using the 143 in the Creedmoor. I'm not trashing the ELD-X, just observing that it was the least spectacular kill I've ever made on a game animal.
The bullet did kill the deer. That is true. It passed completely through also. No blood trail. No catastrophic lung damage. If I hadn't been the one who made the shot, I would have called it a miss and told the shooter to fire again. Going from 26 cal. to 30 cal. is only 44 thousandths of an inch in diameter and it wouldn't make a hill of beans difference if the bullet didn't expand. Just unlucky terminal performance in my case I guess.