Although I think the .243 would kill a deer farther away, 300 yards max is as far as I'd recommend ANYONE take that shot. I have hunted deer with a 6mm for years and have killed dozens with it out to around 300 and I would feel confident taking a shot out to 500 with a bigger gun on a good target, but, if we're all always concerned with the animal itself, than there is just too much possibility of something wrong happening with that small a bullet that far away. I would have shot farther in my youth, but it would not have been the right decision.