To zero a rifle scope efficiently, boresight first, fire three-shot groups, measure the centre of each group, and dial the whole correction in one go: start at 50 m, finish at your zero distance (100 m for most UK centrefire), and confirm with a final group. Done this way, a working zero takes twelve to fifteen rounds.
The most expensive mistake in zeroing is chasing single shots. One round lands low-left, the shooter dials, the next lands high-right, because one shot was never reliable information, and the correction gets reversed. Forty rounds later the scope is roughly where three-shot groups would have put it in twelve. With centrefire ammunition at current prices, method is money.
Key takeaways
- Boresighting costs nothing and gets your first shot on paper at 25 to 50 m.
- Always correct from the centre of a three-shot group, never from one shot.
- A 1/4 MOA click moves impact 7.3 mm at 100 m; a 0.1 MRAD click moves exactly 10 mm.
- A group 70 mm low and 35 mm right at 100 m needs about 10 clicks up and 5 left on a 1/4 MOA scope.
- A box test of about eight rounds checks that the turrets track and return to zero.
Set the rifle up before the range
Half of all "zeroing problems" are mounting problems. Sort these at home:
- Torque the mounts properly. Ring and base screws have values set by the manufacturer, commonly around 15 to 25 in-lb (about 1.7 to 2.8 Nm) for ring caps and more for base screws. Too loose and the scope slides under recoil; too tight and you can crush the tube and bind the internals. A torque driver removes the guesswork. The ring maker's figure always wins.
- Level the reticle. A tilted reticle turns every elevation correction into a diagonal one. Level the rifle in a rest, then level the reticle against a plumb line or with a levelling kit. Even 2 or 3 degrees of tilt shows up as sideways error once you dial for distance.
- Set eye relief and the dioptre. Position the scope for a full sight picture at your natural cheek weld. Allow enough eye relief to avoid scope bite on heavier calibres; most hunting scopes give around 80 to 100 mm. Then set the dioptre (the eyepiece focus) so the reticle is instantly sharp against the sky, and leave it alone.
We do not stock scope rings, scope mounts or torque drivers, only red dot mounts, so source those from a specialist. Our guide to mount height and eye relief covers setup in detail.
Boresighting: get on paper for free
The aim of boresighting is modest: make your first shot land somewhere on the paper at 25 to 50 m. With a bolt-action, remove the bolt, rest the rifle solidly and look down the bore at the target. Centre the target in the bore, then, without moving the rifle, adjust the turrets until the reticle sits on the same point. A laser boresighter does the same job for actions you cannot see through. Neither needs to be better than about 10 cm.
Skipping this step is how people fire six rounds at a 100 m target without a single hole to measure from.
The live-fire sequence
Start at 50 m, finish at 100 m
Fire your first group at 50 m if the range allows. Errors are half the size they would be at 100 m, everything lands on paper, and the sums are easy. Remember that each click moves impact only half as far at 50 m as at 100 m. Once you are centred at 50 m, move to 100 m, the usual UK zero distance for centrefire, and refine.
Three-shot groups, always
Fire three rounds with the same point of aim, from front and rear bags or a proper rest, letting a light barrel cool a little between groups. Find the centre of the triangle the shots make. That centre, not any single hole, is your data point. Chase the group, never the shot.
Dial the full correction in one move
Measure the offset of the group centre from the point of aim, convert to clicks, and dial all of it. Turn the turrets in the direction you want the impact to move: if the group is low and right, dial up and left.
| Click value | Movement per click at 50 m | Movement per click at 100 m | Group 70 mm low, 35 mm right at 100 m |
|---|---|---|---|
| 1/4 MOA | 3.6 mm | 7.3 mm | 10 up, 5 left |
| 1/2 MOA | 7.3 mm | 14.5 mm | 5 up, 2 or 3 left |
| 0.1 MRAD | 5 mm | 10 mm | 7 up, 3 or 4 left |
There is no virtue in creeping towards zero in small steps; the turrets either move the reticle or they do not. For every click value at every distance, see the MOA at distance chart, and for the units themselves, MRAD vs MOA explained.
Confirm, then leave it alone
One final three-shot group centred on the point of aim confirms the zero. If your chosen zero is 100 m, stop there. Some stalkers prefer to zero about 25 mm (1 inch) high at 100 m to extend the point-blank range of a flat-shooting load. If you do, do it deliberately, based on your load's trajectory, and write it down.
The checks most people skip
Parallax and cheek weld
On scopes with side focus or an adjustable objective, such as the Burris Signature HD 3-15x44 (25 yards to infinity, according to Burris), set the parallax for your shooting distance: the reticle should stay still on the target as you move your head slightly. Fixed-parallax hunting scopes are usually set at around 100 yards, and rimfire models such as the Burris Droptine 3-9x40 Rimfire at 50 yards. That is fine, but it makes a consistent cheek weld more important. With your eye off-centre, parallax at other distances can add centimetres of spread that gets blamed on the rifle.
A quick tracking check
Before trusting the turrets in the field, spend about eight rounds on a box test at 100 m. Shoot a group, dial 20 clicks up and shoot, 20 right and shoot, 20 down and shoot, 20 left and shoot. On a 1/4 MOA scope each leg of the box is about 145 mm at 100 m, so use a big target. The last group should land on the first. Groups that do not come back, or a box that is not square, show a scope that does not track true. Reputable rifle scopes pass this routinely.
Ammunition discipline
A zero belongs to one load. Different bullet weights and velocities from the same barrel can print 5 cm or more apart at 100 m, so zero with the ammunition you will actually use. For a stalking rifle, that means your hunting load, not the cheap practice box. If you use two loads seriously, record the offset between them rather than re-zeroing back and forth. And if a rifle that held zero suddenly does not, check the ammunition batch before blaming the scope.
A sensible round budget
| Stage | Rounds | Purpose |
|---|---|---|
| Boresight | 0 | On paper at 25–50 m without firing |
| First group at 50 m | 3 | First data point, coarse correction |
| Refine at 100 m | 3–6 | Fine correction at the zero distance |
| Confirmation group | 3 | Prove the zero before you trust it |
| Optional box test | 8 | Check turret tracking on a new scope |
That is twelve to fifteen rounds for a working zero, or about twenty with the tracking check. If you are using more, the cause is almost always one of three things: chasing single shots, a loose mount screw, or an unstable rest.
Keeping the zero
Zeros rarely wander on their own; they get moved. The usual causes are mount screws loosening under recoil (mark them with a paint pen and check with the torque driver each season), a knock in transit, and changed ammunition. Re-confirm with three rounds at the start of each season and after any drop or journey. For a stalking rifle this is basic fieldcraft: dawn is the wrong time to discover a 10 cm shift. The low-light scopes in our deer stalking scope range deserve the same care as the rifle beneath them.
After confirming zero, photograph the target with the date and load written on it. A season of those photographs is a maintenance log and a diagnostic history in one.
UK note
UK zero distances are usually metric: 100 m for centrefire and often 50 m for rimfire. Most American manuals and ballistic tables use yards, and 100 m is about 109 yards, so a "1 inch per click at 100 yards" figure is wrong at a metric range. Use millimetres at metres throughout. Red dot owners should follow our separate red dot zeroing guide.
Frequently asked questions
What distance should I zero my rifle scope at?
100 m is the usual UK distance for centrefire and suits most stalking calibres. Rimfire rifles are usually better zeroed at 50 m because of their steeper trajectory.
How many clicks is 5 cm at 100 metres?
About 7 on a 1/4 MOA scope, because each click moves 7.3 mm at 100 m. On a 0.1 MRAD scope it is exactly 5 clicks. At 50 m, each click moves half as far, so you need twice as many.
Why does my zero change between sessions?
In rough order of likelihood: mount screws loosening, the rifle taking a knock, a change of ammunition type or batch, and an inconsistent cheek weld combined with parallax. A fault inside the scope is the least common cause, and a box test will confirm or clear it.
Do I need a torque driver to mount a scope?
It is strongly recommended. Ring cap screws are commonly specified at around 15 to 25 in-lb, and both over- and under-tightening cause real problems. A basic torque driver is cheaper than diagnosing either fault with ammunition.
Shop this guide
- Rifle Scopes — MOA and MRAD scopes, with click values in each listing.
- Deer Stalking Scopes — hunting scopes for 100 m zeros.
- Rimfire and .22LR Optics — scopes set up for 50 m shooting.
