A bore sighter aligns your sights with the barrel so your first live round lands on the paper instead of somewhere in the dirt. It is a pre-step, not a zero. Done well it saves the rounds and the frustration normally spent hunting for that first hole.
The three common types, visual through the bore, magnetic or arbor units, and laser cartridges, do the same job with different trade-offs. None accounts for how your ammunition actually flies, which is why live fire always follows.
What a bore sighter actually does
Your barrel points one direction. Your scope points another. On a freshly mounted optic those two can be surprisingly far apart, because the scope sits above the bore, the rings may not be perfectly centred, and the mounting surface has its own tolerances. Nothing about assembling a rifle and an optic guarantees they agree.
Bore sighting makes them agree approximately, before you spend ammunition making them agree precisely. Every tool on the market is just a different way of answering one question: where is the barrel pointing? What none can do is account for anything after the bullet leaves the muzzle: your load’s velocity, the bullet’s drop, or where your cheek weld puts your eye. Only live fire measures those, and that work is covered in our guide to how to sight in a scope.
Bore sighting saves ammunition and time. It does not replace shooting. A rifle that has only been bore sighted is not zeroed and should never be taken afield on that basis. It is the step that makes your first live round useful.
Safety: a firearm is in your hands
Bore sighting usually happens indoors, at a bench, in a relaxed frame of mind. That is exactly how negligent discharges happen, and one of the methods below involves deliberately inserting an object into the chamber.
Confirm the firearm is unloaded. Drop the magazine, lock the action open, and check the chamber both by sight and by touch with a finger. Then remove all live ammunition from the room entirely, not just from the bench. A laser cartridge bore sighter is shaped like a round and goes into the chamber, and you must never be in a position where a live round and a training device can be confused. Keep the muzzle pointed at something you are willing to destroy for the whole session, never at a wall you share with another room, and never at anyone.
When you finish, remove the device before anything else, then confirm the chamber is clear again. A laser cartridge left in a chamber has ruined more than a few rifles when someone chambered a real round behind it. If the rifle is one you also keep loaded, reload it as a separate, conscious step. Our AR-15 home defense setup notes cover the same principle applied to storage.
Visual bore sighting down the barrel
The oldest method costs nothing. It works on any firearm you can see straight through from the rear, which in practice means bolt actions with a removable bolt, most break actions, and some single shots. It does not work on a semi-automatic or a lever gun with a solid receiver.
- Clear the rifle and remove the bolt
Magazine out, chamber checked by sight and touch, ammunition out of the room. Then pull the bolt.
- Rest the rifle solidly
Sandbags, a cradle or a vice. It must stay still while you move between the bore and the scope, or the exercise is pointless.
- Pick a distant, distinct object
Something with a hard edge you can centre on, in a safe direction. Further is better, because a small angular error matters less the further out you reference.
- Look through the bore from the rear
Adjust the rifle in the rest until the object sits genuinely centred in the circle of the bore, not just visible in it.
- Without moving the rifle, look through the scope
The reticle will almost certainly be somewhere else. That gap is the misalignment you are here to fix.
- Adjust the turrets until the reticle sits on the object
Then check back through the bore, because it is easy to bump the rifle while working turrets.
It is free and has nothing to go out of calibration. The limits: see-through actions only, and your eye centring the bore is imprecise.
Magnetic and arbor bore sighters
These are the traditional gunsmith tools. An arbor bore sighter uses a calibrated rod sized to your bore diameter, inserted into the muzzle, holding a grid pattern in front of the objective. A magnetic bore sighter skips the rod and attaches to the muzzle face by magnet, so one unit fits many calibres. Either way you adjust the reticle to the grid’s centre indoors, with no downrange view at all.
Arbor units are precise because the rod is matched to the bore, but you need the correct arbor per calibre, and a sloppy one introduces exactly the error you were trying to remove. Magnetic units are more convenient and calibre-agnostic, but they reference the muzzle crown rather than the bore, so a crown that is not square to the bore axis adds a small angular error.
Laser cartridge bore sighters
The most common tool now, and the easiest to misuse. A laser cartridge is machined to the dimensions of a specific cartridge, with a battery and a laser diode inside. You chamber it as you would a round, close the action, and it projects a dot along the bore axis. A muzzle-inserted variant, a laser on a small arbor, avoids the chambered-device concern at the cost of the same arbor fit issue.
Why the chambered type deserves extra respect
It looks like ammunition, it lives near ammunition, and it goes into a chamber. Store it separate from live rounds, in a marked case, and announce to yourself what you are chambering. Remove it the moment you finish and confirm the chamber is empty.
Getting a usable result from a laser
Two things ruin laser bore sighting. The first is distance. Indoors at 10 or 15 feet a small angular misalignment is invisible, and you end up adjusting the scope to a dot that is not really where the barrel points at 100 yards. Put the target as far away as you safely can.
The second is the dot’s own concentricity. Cheap laser cartridges are not always aligned with the case body. Hold the rifle solidly, rotate or reseat the cartridge a few times, and watch whether the dot moves. A dot that traces a circle is telling you the laser is off the bore axis, and the centre of that circle is closer to the truth than any single position.
| Type | How it references the bore | Strengths | Limits |
|---|---|---|---|
| Visual, down the barrel | Your eye, through the bore itself | Free, nothing to calibrate | See-through actions only, and your eye centres the bore by feel |
| Arbor bore sighter | Calibrated rod matched to bore diameter | Most precise mechanical tool, works indoors | One arbor per calibre, and a loose arbor adds error |
| Magnetic bore sighter | Magnet on the muzzle crown | Fits many calibres, fast to fit | References the crown not the bore, needs a ferrous muzzle |
| Laser cartridge | Chambered device projecting along the bore | Cheap, quick, works on closed actions | Chamber safety, varying concentricity, short distances hide error |
| Muzzle laser on an arbor | Laser held in the muzzle by an arbor | Nothing goes in the chamber | Same arbor fit issues, and the laser can be off axis |
Scroll the table sideways to see every column.
Which type suits which rifle
The action decides most of it. If you can see through the bore with the bolt out, the free visual method is competitive, so try it first. Otherwise the question is whether you want something in the chamber or on the muzzle.
Reach for a laser cartridge when
- The action is closed and you cannot look down the bore
- You own several rifles in the same chambering
- You have a long enough safe indoor distance to use it properly
Reach for a muzzle-mounted unit when
- You would rather nothing cartridge-shaped went in the chamber
- You have the correct arbor, or a squarely crowned ferrous muzzle
- You want a grid to read rather than a projected dot
How close does it really get you
Close enough to be on a reasonably sized target at a short distance. That is deliberately vague, because the result depends on which tool you used, how carefully you fitted it, how far your reference was, and how high the scope sits above the bore. A careful bore sight can put your first shot on a large backer at 25 yards. A rushed laser at 12 feet against a garage wall might leave you well off at 100.
Note also what it aligns. Bore sighting makes the sight line and the bore line converge at a point. Your bullet travels a curved path and crosses the line of sight twice, so even a perfect bore sight does not put point of impact on point of aim. It just keeps the two lines from diverging wildly. The practical target: on paper at 25 yards with the first shot.
The handoff to live fire
Once bore sighted, remove the device, confirm the chamber is clear, and go shoot. Start at 25 yards with a large backer so a first shot that is well off still leaves a hole you can find. Fire one round, confirm it is on paper, then shoot a three-round group and correct from the centre of that group rather than from a single hole. From there it is normal zeroing work: correct, confirm, move to your final distance, confirm again. With a thermal optic the equivalent starting problem is that you cannot see a paper target at all, which our guide to sighting in a thermal scope handles separately.
One small thing that pays off on a long range day: how you carry the rifle back. A sling keeps both hands free for a range bag and a spotting scope, and a two point sling is the usual answer for a rifle you also shoot from supported positions. Our best AR slings roundup covers it.
Frequently asked questions
Is a bore sighter the same as a zero?
No. A bore sighter aligns the sight line with the barrel so the first live round lands on the target. A zero is the relationship between your point of aim and your point of impact at a specific distance with specific ammunition, and it can only be established by shooting. Never hunt on a bore sight alone.
How much ammunition does a bore sighter actually save?
The saving is in the rounds you would otherwise spend just finding the paper. Instead of shooting, missing the backer, guessing a direction and repeating, you start close and go straight into the correct-and-confirm cycle.
Can I bore sight a semi-automatic rifle?
You cannot look down the bore of one, because the action is not see-through with the bolt in place. A chambered laser cartridge or a muzzle-mounted unit both work. Clear the rifle, remove all ammunition from the area, and keep the muzzle in a safe direction throughout.
Does the type of bore sighter change my final zero?
It should not. The final zero is set by live fire regardless of which tool got you on paper. If one consistently leaves you far off, check the arbor fit, the crown, or the laser’s concentricity before blaming the scope.
