Blaine,
I've always managed to have a lighter than "recommended" gun in my hand when elk hunting. The closest comparisons I can make are these:
I killed a huge bodied bull with a .270 WSM 130 Gr. TSX last fall. Blew through both shoulders at over 350 yards but he still pushed himself into the timber about 40 yards away.
I killed two smaller elk this year a .264 Win Mag with 140 gr Partitions. Penetrated both shoulders, and made some big holes.
Both these loads have smaller entrance holes, but have even less weight but similar velocities to your 150 gr .30-06 at 3100.
Oh and I did have a 150 gr Nosler Partition completely penetrate a bull elk's shoulders out of .280 from about 50 yards. So that's 150 grains, less stoutly constructed and a little slower (2800 fps) doing what you're looking for.
Here's the .270 WSM 130 TSX bull:
[Linked Image]


"For some unfortunates, poisoned by city sidewalks ... the horn of the hunter never winds at all" Robert Ruark, The Horn of the Hunter