Here is how to sight in a scope, whatever the optic is bolted to: confirm the firearm is unloaded, tighten and level the mount, bore sight to get roughly on paper, then shoot a three shot group at 25 yards from a solid rest. Measure from the center of that group, dial the correction using the click value printed on your turret, then move back to 100 yards and repeat.
Finish with a confirmation group that you do not adjust. That last group is the only one that tells you whether the zero is real, because everything before it was you chasing holes.
What you actually need
The list is short. Most range-day frustration comes from missing one boring item on it, not from a bad optic.
- A solid rest: bags, a bipod with a rear bag, or a purpose-built shooting rest. A rolled-up jacket is better than nothing and worse than everything else.
- Enough ammunition of one type. Mixing loads mid-session invalidates everything you have measured.
- Targets with a defined aiming point and a printed grid, which saves you measuring in the wind.
- The driver or wrench that properly fits your rings and bases. One that cams out of a screw head is how mounts end up loose.
- A notepad, for the click counts and the load.
- Eye and ear protection, plus binoculars if there is no target retrieval system.
Notice what is not on that list: a laser, a collimator, an app. Those help, but none are required.
Safe setup before the first round
Remove the magazine, lock the action open and physically look and feel inside the chamber. Confirm it is empty before you touch a mount screw, a turret, or a bore sighting tool. Keep the muzzle pointed in a safe direction the entire time.
Only shoot at a range or a location with a backstop that will positively stop your rounds, with a clear view of what lies beyond the target. Follow the range’s rules on cold and hot lines and never handle the firearm while anyone is downrange. On private land, know your terrain and the maximum range of your cartridge.
Set the bench up so the gun points naturally at the target with your body relaxed behind it. If you are muscling it onto the aiming point, that tension will move your shots and you will spend the day dialing out your own posture instead of the scope.
Set the target square to the shooting position and at a height that lets you get behind the optic without craning your neck. A target too low forces you to lift your head off the stock, and an inconsistent cheek weld produces vertical stringing that looks exactly like an elevation problem.
Bore sighting to get on paper
Bore sighting is not zeroing. It is a shortcut that saves a few rounds and a lot of confused staring at an unmarked target. Three common methods:
Optically, through the bore. On a bolt action, take the bolt out. Rest the rifle so it holds itself still, center the bore on the aiming point, then without moving the rifle move the reticle to the same point with the turrets. Costs nothing, and more accurate than most people expect.
With a laser or a collimator. A chamber or muzzle laser projects a dot and you dial the reticle onto it. Both carry their own alignment error, which is why they get you on paper rather than zeroed.
By shooting close. On anything you cannot see down the bore of, put a large backer up at 25 yards and take one carefully aimed shot. Now you know where the gun prints, which is all bore sighting was ever going to tell you.
Staple your target to a wide piece of cardboard. A first shot that misses a small target entirely tells you nothing except that you missed. The same shot on a large backer tells you how far off you are and in which direction, which turns your second shot into a correction instead of another guess.
The first group at 25 yards
Twenty-five yards is the working distance for getting the scope roughly right. Wind is negligible, position errors are compressed, and you can see your own holes without walking anywhere.
- Foul the barrel
If you have just cleaned it, fire two shots and ignore where they land. A clean cold bore often prints away from the group that follows, and zeroing to those rounds gives you a zero that will not repeat.
- Shoot three rounds at the same aiming point
Same hold, same aiming point, same pace. Do not adjust for where the last one went. You are trying to find out where the rifle prints, and one shot cannot tell you that.
- Make the line safe and go look
Find the center of the three holes, not the best one. If they are spread wide at this distance, the problem is the rest or your position, and adjusting the scope only bakes that error in.
- Measure the offset in inches
Measure horizontally and vertically from your aiming point to the center of the group. Write both numbers down with their direction, for example three inches low and two inches right.
- Dial windage first, then elevation
Correct one axis at a time so you can tell what each adjustment did. Turret caps are marked with the direction that moves point of impact, so turn toward where you want the bullets to go.
- Fire another three and check
If the group moved the direction and roughly the amount you expected, the scope is tracking and you can move back. If it went the wrong way, you turned the turret backwards, which is normal and costs you thirty seconds.
Resist the urge to make 25 yards perfect. You are not zeroing here, only getting close enough that a 100 yard target will have holes in it.
Moving out to 100 yards
One hundred yards is where a rifle zero actually gets set, because it is far enough to reveal what 25 yards hides. A quarter inch of misalignment at 25 becomes an inch at 100, and a group that looked tight up close often opens into something more honest.
Zeroing at 25 yards
- Fast, cheap and possible at almost any range
- Wind and mirage are effectively out of the equation
- Hides your real group size, and small errors here multiply at distance
Zeroing at 100 yards
- The distance most ballistic data is published against
- Shows your true group size and real consistency
- Needs a hundred yard range, calm conditions and more rounds
Shoot a three shot group at 100, again from the rest, again without correcting between shots. Measure from the center, dial, then shoot another three to confirm the correction landed where you asked.
Whether your zero should sit dead center, an inch or two high, or somewhere else depends on your cartridge, your optic height and how far you intend to shoot. Use published data for your actual load rather than a number you half remember. What matters here is the process: measure from the group center, dial, confirm.
Reading the turrets and correcting
Every scope tells you what one click does. It is printed on the turret cap or engraved on the turret: a quarter MOA per click, a tenth of a mil per click, or a fixed fraction of an inch at a stated distance. Read yours instead of assuming, because the assumption is where corrections go wrong.
The rule that survives every optic: your click value is stated for a specific distance and it scales with distance. A click that moves the bullet a quarter inch at 100 yards moves it half an inch at 200 and a sixteenth of an inch at 25. Correcting at 25 yards therefore takes roughly four times as many clicks as the same correction at 100.
Count clicks out loud and write down what you dialed. When a correction does not land where you expected, that record tells you whether the scope failed to track or you lost count. Most of the time it is the count.
The arithmetic behind MOA and mil clicks, with worked examples, lives in our companion piece on how to sight in a rifle scope. Crossbow optics behave differently enough to warrant their own read: see how to use a crossbow scope and how to sight in a crossbow.
Confirming the zero
A zero is not finished when the group is centered. It is finished when you can shoot a fresh group on a different day, without touching anything, and have it land where the last one did.
Shoot a final confirmation group and leave the turrets alone regardless of what it shows. If it lands where you want, you are done. If it does not, you have learned something more useful than another correction: either the mount is moving, the load is inconsistent, or your position is not repeatable.
Then confirm from the positions you actually use. Kneeling, prone or off a barricade will each show a slightly different picture, and that is your shooting rather than your scope. It is also where a sling earns its place: run into a hasty loop or take up tension on a two point sling and a wobbling position steadies noticeably. Our guide to the best AR slings and the piece on the two point sling for AR15 cover setting the length so the loop is usable.
Where people lose the afternoon
| What you see | Usual cause | What to do |
|---|---|---|
| Groups are wide and round at any distance | Position and rest, not the optic | Rebuild the rest, relax behind the gun, fix the cheek weld |
| First shot from a clean barrel lands away from the group | Cold clean bore behaves differently to a fouled one | Fire two fouling shots before you record anything |
| Point of impact walks steadily as you shoot | Loose ring or base screw, or a hot thin barrel | Stop, check every screw, let the barrel cool between groups |
| Vertical stringing on an otherwise tight group | Breathing, trigger timing, or an unsupported rear bag | Slow down, add a rear bag, break the shot at the same point each time |
| Tight from the bench, wide from field positions | Your body is now the rest | Practice supported positions and use sling tension to stabilize |
Scroll the table sideways to see every column.
After the session, write down the load, the distance, the conditions and the final dial position. Next season that page answers questions you cannot otherwise answer.
Frequently asked questions
How many rounds does it take to sight in a scope?
Budget 15 to 25 for a fresh mount, and closer to 5 to confirm an existing zero. Work in three shot groups. Past 30 rounds and still chasing the group, stop turning turrets and check the mount, the rest and the ammunition.
Can I sight in at 25 yards and skip 100?
You can get very close at 25, and for some setups that is enough. But 25 yards hides both your real group size and small errors that grow with distance, so confirm at the distance you intend to shoot before you trust the zero.
Do I have to bore sight first?
No. Bore sighting saves ammunition and time, and that is all it does. If you cannot bore sight, put up a large backer at 25 yards and let the first shot do the same job.
How often should I re-check my zero?
Before a season, after travel, after the firearm is knocked over, and any time you change ammunition, optics or mounts. A three shot group answers it in minutes.
More on zeroing and optics
- How to Sight In a Bow and Arrow: Starting From Scratch
- How to Sight In a Compound Bow: Pin by Pin
- How to Sight In a Red Dot on a Pistol
- How to Sight In a Red Dot: Zeroing Without Magnification
- How to Sight In a Rifle Scope: Mounting, Torque and Turrets
- How to Sight In a Rifle: Iron Sights or Optic
- How to Sight In a Thermal Scope
- Sighting In a Muzzleloader
- Sighting In an Air Rifle
- The 100-Yard Zero for Hunting Rifles
- The 25-Yard Zero: Why It Works and When It Does Not
- Three-Pin Bow Sights: Setting Each Pin
- Using a Bore Sighter: Saving Ammo on the First Zero
