No, it's not pure luck.
Most awesome sniper rifles have a MOA of .1-.2 . This means that at 100 yards, you can draw a circle with .25 diameter and all the bullets would land within this circle (assuming they are small enough to fit in).
However, it also means that at 200 yards, that circle gets big enough to fit all the bullets in .4 diameter circle. At 500 yards, this gets to be 1 inch diameter circle.
Now this is a perfect gun with perfect ammo. It doesn't exist in the real world without plopping down thousands of dollars.
.25 MOA is very good to obtain in the real world. So that means at 2800 yards, the Bullet would land within a 700 inch circle. Now, this might seem easy itself, it is not. You have to worry about windage, heat differences and all this stuff. If you can hit this 700 inch circle at 2800 yards, you are really really good.
However, hitting a 24 inch wide person at that distance is all luck.