I've seen several bull elk killed with the 168 Berger hunting bullet, one was at 50 yards day dreaming when a buddy put one through his shoulder with the bullet traveling at a step angle up the base of his neck and ending up under the hide on the neck. He's killed probably close to 15 animals with them all one shot down and most exiting.
I load for a guy with a 7mag and since the shooter tends to shoot elk in the front end I loaded the 168 Target bullet, last year he killed four animals ranging from bull and cow elk to deer, one real nice muley buck took one from one hip through his body and exiting his opposing front shoulder, very nice wound channel and he didn't argue, ranges were from under 100 to just over 500 yards.
IMO if a Berger is opening on the surface with a large entrance then something is weakening the jacket be it heavy fowling, a rough throat or velocity. If a Berger is working normal and jacket integrity is good the entrances I've seen are hard to find with very little evidence of opening for a couple inches sometimes more. I would try a Berger Target and shoot something with it to compare, that may shed some light on what is happening. A couple elk guides around here have switched to the 168 Target bullet for elk.