Jayjay, i'm not quite sure of your fixation in shooting at 300yds. Will the cartridge/rifle do it, well most certainly if it is pointed in the right direction and the slug lands in the right spot it WILL no doubt kill. Should you attempt it ??? Do you have the skill, confidence, knowledge of the trajectories ? Only you can answer that. I'm sure that you, like all other ethical hunters, have a deep seated moral and ethical commitment to making sure that any attempted shots on game are taken with a serious commitment to avoiding losing wounded animals. If and when you are unsure whether to get closer or pass the shot to me that alone suggests enough doubt to do both, pass or try get closer. An unalarmed animal that has not been fired at lives to be hunted another day.