Which zero?

Your sight line is straight. Your bullet's path is a curve. The barrel is angled slightly upward relative to the sight line so the two intersect, and because one is straight and the other curves, they intersect twice.

The first crossing is the near zero, on the way up. The bullet then rises above the sight line, reaches an apex, and comes back down to cross again at the far zero. Past that it keeps dropping.

When someone says "100-yard zero," they mean the far crossing. The near crossing exists whether or not they mention it, and on some setups it matters a great deal.

Height over bore

The distance between the centre of the bore and the centre of your optic determines how much of a correction the barrel angle has to make, and therefore where the near zero lands.

• AR-pattern rifle: roughly 2.5 inches, sometimes more with a taller mount.
• Bolt-action with low rings: roughly 1.5 inches.
• Pistol with a slide-mounted red dot: roughly 1 inch.

The practical consequence is at close range, and it surprises people. With a 50-yard zero on an AR, a shot at 10 yards impacts roughly two inches below your point of aim — not because of drop, but because the bullet hasn't yet risen to meet the sight line. On a small target at close distance that's the difference between a hit and a miss, and it's the reason close-range holdover is taught as a specific skill.

The common zeros

50 yards (AR-pattern)

The default for a general-purpose carbine, and for good reason. With typical 5.56 loads it produces a second crossing somewhere near 200 yards, and between those two points the bullet stays within a couple of inches of the sight line. That means point-of-aim, point-of-impact for practical purposes from the muzzle out past 200 yards, with no holdover thinking at all.

The exact far crossing depends on your load, barrel length and mount height. Treat "50/200" as a description of the concept, not a guarantee — confirm yours on paper at distance.

100 yards

The standard for centrefire bolt guns and the sensible default for anything you'll dial. It's far enough to be meaningful, close enough that wind is negligible while zeroing, and it's the input every ballistic solver expects. If you range targets and dial the solution, a 100-yard zero is simply the cleanest reference point.

200 yards

Popular for hunting rifles because it flattens the useful trajectory. Many common centrefire hunting cartridges zeroed at 200 stay within about three inches of the sight line from the muzzle to somewhere past 250 yards, which covers the large majority of field shots with no holdover at all.

25 and 36 yards

Short-range zeros used as approximations of much longer far zeros — the idea being that you can establish a usable long-distance zero on a short range. They work, roughly, but the approximation is sensitive to load, barrel length and mount height, and small errors at 25 yards are magnified enormously at 300. Use them to get on paper, then confirm at the actual distance before trusting them.

Maximum point blank range

This is the concept that ties it together, and it's more useful than any specific zero number.

Decide how much vertical error you'll accept — say a six-inch circle, meaning three inches above or below your aim. Maximum point blank range is the furthest distance at which the trajectory stays inside that window, given a zero chosen so the apex just touches the top of it.

Inside your MPBR you aim dead centre and hit, with no holdover and no dialling. Past it you have to do something deliberate. For a typical centrefire hunting cartridge with a six-inch window, MPBR commonly lands somewhere in the 250–300 yard region — which is beyond most field shots.

This reframes the question usefully. Rather than "what zero should I use," ask "how big is the target I need to hit, and how far do I need point-and-shoot to work?" The zero falls out of the answer.

Choosing

Confirm it, don't calculate it

A ballistic solver will predict your near and far crossings accurately given correct inputs — and the inputs people get wrong are muzzle velocity (which varies with your barrel, not the box) and height over bore (which people estimate rather than measure).

Measure your height over bore properly. Chronograph your load if you can. Then go and shoot the distances that matter and write down what actually happened. The paper is the authority; the solver is a prediction. And once you've set the zero, verify the scope actually tracks before you trust any dialled solution built on top of it.

FAQ

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