Ditto what Stubblejumper said. Unless you break both shoulders a mature elk will still run for a short distance.
Unless it's the only shot presented I never purposly aim for the shoulder on an elk, or anything else for that matter. I always aim to hit right behind the shoulder and get a good double lung shot and usually a complete pass thru. Besides that, A double lung shot elk will generally run down hill and that is good where I hunt. Even if it's only 40 or 50 yards.
Having said that a 180 grain Nosler partition is a bullet that is certainly capeable of breaking both shoulders should you hit both of them. Your friend doesn't sound like he has a clue.
