Interesting. For a couple seasons I used a 6.5-300 Wby with 127 LRXs. Only bullets I recovered were out of a moose shot at 18 yards. Barely expanded, maybe 25% bigger frontal surface than the bullet’s original shape. And I know for a fact they were impacting at ~3400 fps.
Killed it just fine but I was underwhelmed by how the bullet looked.
As far as my 2 cents on the .30-06 at 400 yards on elk, by the time you have the experience to qualify you to take a shot like that, you’ll have learned the answer. Unfortunately for the animals, people don’t always stay within their limits. Rarely is an animal wounded, lost, or missed due to a cartridge problem.