This^
What matters more then anything else, is shot placement. Doesnt matter if its my 300rum, 375H&H, 45/70, or 30/30, poor placement will net the same results. Shoot whatever caliber you feel most comfortable with, and shoot it often. 3 shots to sight it in this october does not qualify either,lol. Though I wouldn't use a 243, a good shot with a 243 is better then a mediocre, or average shot with a 300win.