For purposes of this discussion, we’ll assume that we’re talking about a .223 Remington or 5.56mm caliber rifle, although at shorter distances, it really doesn’t matter as you’ll soon see.
Since the whole idea of zeroing is to line up your sights with the impact point of a bullet, you can set your “zero” just about wherever you want. But first, remember that the sightline is 2 ½ inches (give or take depending on your equipment) above the bore. For purposes of this discussion, our examples will assume we’re using a standard 55 grain .223 Remington cartridge.
- If you set your zero close, say at 10 yards, you will have to align your sights so that the barrel points up very aggressively relative to the sight line. The barrel has to be angled up pretty severely for the bullet to move up 2 ½ vertically in such a short distance. As a result, after the bullet crosses the 10 yard zero, it will keep traveling upwards. Farther down range, say at 100 yards, the bullet will be 20 inches above your line of sight.
- If you set your zero at 50 yards, the angles are less severe. The barrel is angled less aggressively towards the line of sight. With a 50 yard zero, your bullet will only be about 1.57 inches above the line of sight at 100 yards and height maxes out just over 2 inches above around 150 yards. From then on, it’s all down hill again.
- If you set your zero at 100 yards, the bullet slowly arcs up to intersect the line of sight way down range. Coincidentally, with a 100 yard zero, the bullet never really travels above the line of sight. As soon as it intersects the line of sight at 100 yards, it starts the downward fall again.
As you can see, you have some decisions to make depending on how you anticipate shooting. If every single target you will ever shoot will be at the exact same distance, then set your zero for that distance. However, this is kind of unrealistic. Most people will need to be able to hit targets at different ranges, so you need to compromise.