There is nothing wrong with a 7mmMag.Apparently you had bad shot placement.If you hit them right they will go down.I blew the heart and lungs out of a 7 point a few years back.The brush was covered in frothy blood and lungs. He still managed to run a good 75 yards before dropping.Then there has been others that drop in their tracks.Take your time and make sure of your shot placement.It's easy to blame the gun and cartridge when in reality it's human error.

Ruger Redhawk