You need a different guide - anything from a 7 MM up with the proper bullet put in the proper place will drop em. A 300 will certainly do the trick. I've found that any animal with its adrenaline up will stay on its feet a few seconds longer than an unalert animal. My gunsmith told me of a bull elk that was taken by his father in British Columbia. This hunter was a world class benchrest shooter and he and the guide got to within 500 yds of a nice bull. The first shot was a picture perfect shot behind the shoulder. The bull's head started to drop after a few seconds and the guide sent a challenging bugle towards the bull. The bull postured up alert and ready to fight. The hunter seeing the bull staighten up immediately sent another round right next to the first. again the bull's head started to lower. The guide sent another challenge towards the bull and again the bull postured up and looked around for the challenger. Before a third round could be sent, the guide stopped the shot and said no more would be necessary. The bull fell over about 8-10 seconds later. I know I've made some really bad shots before, but because the animals never knew i was there, they fell in their tracks. Other times I've had animals run nearly 100 yds from perfectly placed shots when the animal was being chased.