Re: 178 gr A-max question.
I tested some 168gr Amax out of my Wby at 70yds. Impact vel was around 3100fps. This bullet went through 2 gallon milk jugs and speckled the third. The two milk jugs were vaporised. The third leaked badly.
By comparison, a Nosler BT went through three jugs. Vaporised the first two and split open the third.
The 178gr would probably go through all three jugs. Easy test for you to do.
For hunting elk, I would consider shoots from 150yds out. The further the better. High vel impacts that have to break bone may not be so good. However, through the rib cage, you may not have to do much gutting. Just pore out the inards.