The 20-Shot Zero: Stop Walking Away With a Near-O

Most shooters leave the range with what one precision rifle shooter calls a “near-o” rather than a true zero. Too few rounds go downrange, and the scope corrections that follow are not precise enough to trust. The fix is a sampling method that pools roughly 20 shots into a single dataset before you touch a turret, which lets you make one accurate correction instead of a string of guesses. This guide covers the full process: hardware check, bore sighting, confirming your mechanical offset, building the 20-shot aggregate, making a single adjustment, and recording the result.

The gear list is short. For the aggregation work, you need a paper target with a 1-inch grid, a clean sheet of blank paper the same size, something pointy for poking holes, and fine-point markers. Rounding out the kit are a torque wrench, a spotting scope or binoculars, a laser bore sighter, a rangefinder, calipers for measuring groups, and a ballistic calculator. A stable platform matters too, so use a bench with bags or a bipod with rear support. Sight in with the exact load you intend to shoot, since a change in bullet weight or velocity moves your point of impact.

Step 1: Check and torque every screw

Go over the hardware before you fire a round. On a new rifle or after mounting a fresh optic, start by checking every fastener: action screws, mount screws, and ring screws. A mount that shifts drags your zero with it, so none of this is optional.

Craig Boddington reaches for a torque screwdriver to keep from over-tightening, and the risk is genuine, because leaning on a fastener too hard can snap it off. Mount makers list recommended torque figures, generally somewhere between 20 and 30 inch-pounds, and you should bring optic mounting screws to those numbers before you zero. Action screws call for a lighter touch. Pull them down too far and you seat the action too deep in the stock, which upsets the bedding, so Boddington treats hand-tight as the right feel for them. While you are in there, check that the rings line up and the reticle sits vertically true.

Step 2: Bore sight to get on paper

The reason to bore sight is to get roughly aligned before you spend ammunition. There are three approaches: an optical collimator, a laser device, and lining things up by eye. The by-eye method works only if you can pull the bolt or open the action and look straight down the barrel, which makes it a natural fit for bolt-actions and a workable option on most single-shots and AR-type rifles with an easily removed bolt. Lever-actions, slide-actions, and some semi-autos block that view, so you lean on a laser or collimator for those.

To do it by eye, pull the bolt, peer through the bore to center your aiming point, then adjust the optic until the reticle sits where the bore is pointed. Keep in mind that your scope adjustments run backward from the bore picture, so a correction that seems to go up actually drops the point of aim, and left reads as right. Bore diameter affects how well this works. A .22-caliber rifle gets you close by eye, while a .30 or a .375 gives much coarser results. Boddington favors bore sighting by eye over collimators or lasers when the choice is his, citing the imprecise results he has gotten from the devices. If you use a laser bore sighter, you drop the laser in and align the reticle to it at 25 yards.

Whatever the method, start short. Boddington’s advice is a big target and the shortest practical range so you get on paper quickly. For rifles he cannot look down, he begins at 25 yards and moves up to 10 if that is still not enough. He papers over the whole target frame with butcher paper, marks an aiming point near the middle, and props the rifle on shooting sticks for those opening shots. Starting at 25 yards spares your ammunition, and a large target with a bold round aiming point lets you bore sight out to 50 yards.

Step 3: Understand the 25-yard offset

Treat 25 yards as a setup and confirmation step rather than a finished zero. It serves to rough-in a new optic and get rounds on paper, nothing more. Because the optic rides above the bore, a zero dialed at 25 yards will land well off the mark at distance, which is why you confirm at your real shooting range later.

The turret math changes with range. A common scope moves ¼ MOA per click, and since 1 MOA is close to 1 inch at 100 yards, correcting an inch at that range takes four clicks. The number of clicks grows as the distance shrinks. At 25 yards with a ¼ MOA scope, moving an inch takes 16 clicks per inch, and at 50 yards, it takes eight. Confirm which distance you are on before you start clicking.

Step 4: Build the 20-shot aggregate

This is the core of the method and the step most shooters leave out. Three- and five-shot groups fall short of the statistical threshold needed to draw accurate conclusions about a rifle. Get the count near 20, and the data becomes something you can lean on. A group at Hornady has driven this testing hard, sometimes firing strings of 100 rounds or more, and Outdoor Life now lists 20-shot group sizes and mean radius in its rifle reviews.

The trick is aggregation. Shoot several groups at a spread of separate aiming points, leaving the scope alone between them, then transfer every shot onto one sheet of paper around a single aiming point. Print the target and a blank sheet both on standard 8½-by-11 paper so their edges match. A soft mat beneath the pair makes it easier to poke each hole through and mark the shot locations on the clean page. What you end up with is a single 20-shot dataset built around one aiming point.

Your discipline here decides the outcome. Give the barrel time to cool between groups. Keep your cheek weld the same shot to shot, settle into the natural pause in your breathing, break the trigger cleanly, and follow through. If the groups scatter, sort out your fundamentals before you reach for a turret. Chasing single shots, hurrying your strings, changing loads midway, and ignoring parallax are the usual ways people ruin a zero.

Step 5: Make one correction, then confirm

With 20 shots pooled, measure where the group’s center falls relative to your aiming point and make one adjustment. That single accurate correction is what gives you a true zero. An app handles the measuring: Hornady’s 4DOF app has a group analysis tool that returns group size, mean radius, and where the center sits against your aim point, available as a $4.99 upgrade. The Ballistic X app offers the same group analysis, at $7.99. Mean radius, the average distance of each shot from the group’s center, is a better predictor of performance than raw group size.

Confirm after you correct. Fire a controlled 3-to-5 round group at your chosen distance, then verify the zero with a longer string of 10 to 15 rounds. Choose the distance by your purpose. A 50-yard zero keeps your holds small inside 200 yards and works well for carbines and general-purpose ARs. A 100-yard zero is the precision benchmark, which keeps the ballistic math and DOPE tracking simple for hunting and precision rifles. A 36-yard zero, the “300-yard battle zero,” keeps trajectory within a few inches from zero to 300 with common 5.56 loads. There is no one best distance.

What a correct result looks like

A true zero puts the reticle and the bullet in the same spot at your chosen distance, proven by a long string rather than a lucky three-round cluster. Write it down: record the load, zero distance, wind, temperature, muzzle velocity, ballistic coefficient, and conditions, and take a photo of the final group.

The errors that unravel all this are predictable. Shooting too few rounds, correcting off single shots, switching ammunition midway, letting the barrel get hot, and skipping the final-distance confirmation all leave you with a near-o. Zero wanders over time regardless, as screws back out, bores wear, and loads shift, so check it before any shot that counts.

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