Pick an AR-15 Zero by the Miss You Can Live With: 25, 36, 50 and 100 Yards Compared

Change any of these and the numbers shift, so they are printed before the tables rather than in a footnote.

• ▸Rifle: 16in barrel, AR-15, red dot on a 1.42in mount
• ▸Sight height above bore: 2.60in (flat-top rail at 1.18in over bore, plus a 1.42in mount)
• ▸Atmosphere: sea level, 59F, 29.92 inHg
• ▸Loads and muzzle velocities from 16in: 55gr M193 at 3,100 fps, 62gr M855 at 2,950, 77gr OTM at 2,750, 300 BLK 110gr at 2,350, 300 BLK 220gr subsonic at 1,020
• ▸Model: point-mass, constant G1 BC (0.243, 0.304, 0.372, 0.290, 0.608 respectively)
• ▸All offsets are point of impact relative to the dot; negative is low, positive is high

Sight height matters more than people expect. Go to a 1.93in mount and every close-range figure gets about half an inch worse, and the maximum ordinate rises slightly. If you run a taller mount, treat the tables below as directionally right and re-solve for your own height before you commit to a hold.

One thing that does not matter much: barrel length between 14.5in and 18in. A 200 fps swing in muzzle velocity moves the second zero by roughly 10 yards and the maximum ordinate by under a quarter inch. The zero decision is robust to barrel length in a way that long-range dope is not.

Read down your chosen zero's column. Positive numbers are impacts above the dot, negative are below.

The 25-yard column is the one to dismiss immediately for rifle use. Ten inches high at 225 yards is not a zero, it is a hold-under you have to remember at every range in between, and the maximum ordinate arrives right in the middle of the band where most people shoot. It survives as a zero because it is a convenient distance to zero at indoors, not because the trajectory is any good. Zero at 25 to get on paper, then move out and finish properly.

The 100-yard column is quietly worse than its reputation too. It is 2.2 inches low at 200 and 10.8 inches low at 300, so you are holding over almost immediately. Its one virtue is that nothing is ever high, which some people find easier to think about.

Heavier bullets shift the curve down and in. Here are the three figures that define each combination rather than the whole grid.

The 77gr load flattens the arc slightly at every zero, which sounds like an advantage and mostly is not at these distances. It buys you 0.9 inches less maximum ordinate at a 36-yard zero and costs you 2.5 inches more drop at 300. Inside 200 yards, the difference between M193 and a 77gr match load on the trajectory is smaller than the difference between two shooters' triggers.

Where the 77 earns its money is past 300 and in wind, neither of which is a zero-distance question. Pick the load on accuracy in your barrel and on what you can afford to shoot; do not pick it for the trajectory.

Supersonic 300 BLK is a different trajectory problem and subsonic is a different sport. Both are on the same rifle, which is what makes the zero choice awkward.

Subsonic 220gr is down 21 inches at 150 yards and over 10 feet at 300. There is no zero that makes that manageable — it is an arc, not a trajectory, and it wants either a ranging reticle or an honest acceptance that it is a 100-yard proposition.

For supersonic 110gr, the 36-yard zero is genuinely good: maximum ordinate 2.4 inches, second zero at 188, and inside 4 inches of the dot all the way to 200. That is a better close-to-mid answer than the 50-yard zero gives on this load, which is the reverse of the 5.56 result. The reason is simply the lower muzzle velocity — the whole curve is compressed, so the optimum near-zero moves in.

Point-blank range is the distance band inside which you can hold dead centre and still hit, given a target size. It has an exact answer: find the launch angle whose maximum ordinate equals half the target, then find where the curve drops through the bottom of the window.

Here is the finding that settles it. On a 6-inch target the 50-yard zero reaches 266 yards against a theoretical best of 289 — you give up 23 yards for a zero distance you can actually set up on a public range. On a 10-inch target the 36-yard zero reaches 336 against a theoretical best of 342, giving up six yards.

So both camps were right the whole time. The 50-yard zero is the correct answer when precision matters and the target is small. The 36-yard zero is the correct answer when the target is generous and you want maximum reach without holding over. They were never disagreeing about ballistics. They were disagreeing about what they were shooting at, silently.

Zero at 50 yards. For nearly everyone reading this, on 5.56, with a red dot, that is the answer. Maximum ordinate under 2 inches means you can hold centre on anything from contact distance to 260 yards and never think about it, and the 222-yard second zero is convenient enough to remember.

Take the 36-yard zero instead if — and only if — your longest realistic shot is past 260 yards, you are willing to accept 4.5 inches high in the middle, and the thing you shoot at is bigger than 8 inches. Practical rifle competitors and people running a rifle as a general-purpose tool at longer distances have a real case here.

Skip the 25-yard zero unless you are following a specific military qualification course that specifies it. It is the highest maximum ordinate of any of them and it delivers that error precisely in the 150 to 250 yard band. And skip the 100-yard zero unless your entire use case is a 100-yard bench, in which case it is fine and the rest of this page does not apply to you.

Most public ranges do not offer 36 or 50 yards. Here is how to get there anyway, and none of it requires a longer range.

• ▸To set a 50-yard zero at 25 yards: aim centre and adjust until the group prints 1.2in LOW at 25 yards. That puts you exactly on at 50 with a 2.60in sight height.
• ▸To set a 36-yard zero at 25 yards: aim centre and adjust until the group prints 0.7in low.
• ▸To set a 50-yard zero at 100 yards: adjust until the group prints 1.6in HIGH at 100 yards.
• ▸Shoot five-round groups, not three. Three-round groups lie about where the centre is, and you will chase them.
• ▸Let the barrel cool between groups. A hot thin-profile barrel walks, and you will zero to a condition you never shoot in.
• ▸Confirm the finished zero at the actual distance if you ever get access to it. The offsets above are arithmetic; your rifle is a physical object.

One habit that saves a lot of ammunition: before adjusting anything, measure the distance from the group centre to the point of aim in inches, then convert to clicks using your turret's value at that range. Guessing at clicks and re-shooting is how a zeroing session turns into forty rounds. Doing the arithmetic once turns it into twelve.