I followed this video to the exact and got the achievement in my first try. The level will be Nambia day 1, hunt 3(zebra). Right after you make your kill in hunt 2, go view the zebra tracks. Now walk back to the tree stand you used in hunt 2. Using your long rifle take a look at the zebra, now just walk backwards till it read 280 yards. You will not be able to see the zebra, and if you miss, the zebra will not move, allowing you to continue shooting till you hit it. Fortunately I got a spine hit on my first shot!
Video credit Bigal4242