"Battle Sight Zero"
Sir:
Your're getting some erroneous information here; if the Bushmaster is anything like the former military M-16. We are discussing 5.56 x 45 mm ammunition aren't we?
Much of the military did sight them in at 25 meters which is an insignificantly more distance than 25 yards.
That is, the targets were 25 meters distance from the shooter. How ever...
The strike of the bullet at the 25m target was not set by sight adjustment to put the holes on center; the bullseye, at that range!
Because of the bullet following a curved path; not quite a great circle, but what is called a parabola, where the initial curviture is gradual and then at a certain range, the curve increases more and more rapidly. A horizontal stream of water discharged from a garden hose will curve similarly to the ground.
So, the sights were adjusted to cause bullet impact, at 25m, to strike
approximately 2 1/2 inches or 6 cm above {but centered} the bullseye of the target.
With the sight adjusted for that "trajectory," you could aim center mass on the enemy less than 250 m and your bullet would be striking high by that 2 1/2 inches or at the further range of 250 m, strike dead center. Bullseye.
Beyond that range is another matter altogether.
I may be off by a fraction of an inch on that, but it will be close.
Now you must memorize how your target appears at 250 m. Eyes visible?
Face visible? Colors visible? That kind of thing.