A well placed 150gr Nosler Ballon Tip would be into the lungs, 2-3" behind the shoulder of a bull elk. At 50 yards that should be a chip shot.
Maybe. I've shot 140gr BT's out of my 7mm Magnum at Coues deer. One buck I took the bullet fragmented with about 8" of travel in the deer's thorax. The range to the deer was about 275 yards. A dead deer for sure.
But 50 yards vs 250 yards, a .300Wby vs a 7mm Magnum, a 500-600 pound animal vs a 100lb animal......I wouldn't bet on it.