ORIGINAL: halcon
I hunt with the 243 Win all the time and wouldn't recommend it on deer over 300 yds . It drops pretty fast beyond 300 yards on a rifle zero'd at 200 yards .
Your obviously using the wrong bullets. Check out federals 100 gr. sierra gameking BT, or even their 85 gr. sierra Gameking HP. They both shoot flatter than just about every non magnum cartridge, with plenty of velocity and enough energy out to 500 yds great BC too, bucks the wind great.