We took 2 elk with the 408/338 (338 Allen Magnum) this year. 520yds and 508yds. We are using the 300gr Sierra Matchking they were not typical entrance/exit wounds, I believe the shot was too close/too high velocity for the SMK on both elk.. Neither elk moved more than 15ft. The entrance wound was about 3" on one elk and the entrance/exit was one hole where several vertabrae were removed on the other.
What amazed me, was the lack of bloodshot meat for both animals, I suspect it was pure luck that we didn't mess up more meat at only 500yds with the 338 Allen Mag.
If some is good and more is better, then too much is just right.
My mind is a raging torrent, flooded with rivulets of thought, cascading into a waterfall of creative alternatives