How to Bore Sight a Rifle Scope Before You Sight-In

Hello and welcome to my guide: How to Bore Sight a Rifle Scope.

Imagine you are at a rifle range with your new scope mounted atop a new rifle. You are there to zero that new scope to that new rifle for the first time.

You have already posted a sight-in target way out at your desired zero distance.

Back at the shooting bench, you aim carefully at the target and take that much anticipated first shot.

Your shooting technique was perfect. You feel confident that you hit the target. All you have to do is adjust the reticle to coincide with the bullet hole in the target.

Now imagine examining the target thoroughly with your spotting scope and not finding a bullet hole. You do not believe you missed that whole target so you walk out to the target between relays for a closer look.

What? No bullet hole. Drat! 

Your scope adjustments were so far off you really did miss the target completely.

You'll have to adjust your scope to move the point of impact to the target before you fire your next shot.

But which way should you adjust your scope?

Did the bullet miss high, low, left, or right? High and left or low and right? How far did the bullet miss? You do not know.

Should you make random scope adjustments and fire more trial shots hoping that a bullet will eventually find the target?

No, that would take too much time. And you do not have ammunition to waste anyway. You could hang a bigger target or even several targets. The next bullet will surely punch paper so you could adjust from there.

Okay; that's enough imagining. In reality you would have boresighted the scope to the rifle even before you tried to sight-in.

Is boresighting necessary? You ask yourself.

Boresighting is a method of aligning the scope reticle with the rifle bore.

The first boresighted shot will probably punch paper and be much closer to the aim point than if you just when to range and started shooting in the general direction of the target and wondering where your bullets are going.

Boresighting will not sight-in your rifle. 

No; it is only a preliminary step to sighting-in a rifle. You still must sight-in because boresighting does not allow for muzzle jump, barrel whip, bullet drop, parallax, and precession.

However, boresighting will prevent a lot of frustration and save a lot of time and ammunition when you do sight-in.

Adjust the scope's eye relief and check the focus and levelness of its reticle before you boresight.

Not sure how to adjust eye relief or focus the reticle? See How To Correctly Adjust Eye Relief and How To Focus A Scope Reticle on this website.

There are three ways to boresight: optically with a collimator, electronically with laser boresighter, and visually.

Optical and laser boresighting both require some kind boresighting tool. Visual boresighting, on the other hand, does not require a special tool.

However, visual boresighting can be done only with bolt action or falling block actions guns and AR-15-style rifles. The breechblock of any other action will obstruct your view of the target through the rifle bore. Also, visual boresighting is the least precise of the three methods.

You should order an optical boresighter or a laser boresighter if the rifle you will be zeroing is not an AR-15-style rifle or does not have either a bolt action or a falling block action.

An optical boresighter or a laser boresighter will still work with a bolt action or falling block action rifle and be more precise than visual boresighting.

I will introduce some proper bore sighting techniques bellow.

How to Bore Sight: Optical Boresighting

If you have an optical boresighting tool such as a collimator, you can boresight at home before you go to the rifle range to sight-in. 

Boresight at home? How to boresight a rifle at home?

An optical boresighter attaches to the muzzle of the rifle either magnetically or with the appropriate size bore arbor.

Follow the instructions of your particular boresighting tool. The instructions explain how to align the reticle with the grid pattern in the collimator.

If your scope mounting system has a windage (left and right) adjustment, use it to make most of the vertical crosshair alignment with the middle vertical grid line displayed in the collimator.

When you have the vertical crosshair as close as possible, use the scope's internal windage adjustment to correct the remainder.

Use the internal elevation (up and down) dial to align the horizontal crosshair with the grid. (The elevation dial is on top of the scope tube while the windage dial is on the right side.)

Normally, the arrows on the scope dials show the direction to turn the dial to move the point of bullet impact to the reticle when you sight-in.

However, since you are moving the reticle to the boresight grid within the collimator instead, the click adjustments work opposite to the directions indicated on the dial.

That is, turn the windage dial counterclockwise to move the reticle left and turn the elevation dial clockwise to move the reticle up. ("UP" moves the reticle down; "LEFT" moves the reticle right.

Yeah, it is confusing. Simply reverse the clicks if you notice the reticle moving in the wrong direction on the grid.)

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How to Boresight At 25 Yards

If you do not have an optical boresighter, you can use an electronic boresighter such as a laser boresighter or you can boresight visually. 

Do laser bore sights work?

Laser boresighting and visual boresighting should be done at the range because you will need 25 yards of unobstructed range to do either correctly. (Actually, laser boresighting and visual boresighting can be done at home if you have 25 yards of unobstructed view.)

Instructions included with certain laser boresighters say you can boresight between 50 and 100 yards if you can see the laser spot on your target that far. However, twenty-five yards is the best distance to boresight.

1/4-inch clicks per 100 yards are worth only 1/16-inch at 25 yards

1/4-inch clicks per 100 yards are worth only 1/16-inch at 25 yards

Why is 25 yards the best distance to boresight? Because the shooter's line-of-sight (LOS) to the target coincides with the bullet's trajectory at two distances: at the zero distance and somewhere around 25 yards.

Obviously the bullet coincides with the LOS where it impacts the target at whatever range the rifle is zeroed for.

However, on its way to the target, the bullet just happens to rise through the LOS at about 25 yards first.

You see, the bullet departs the muzzle below the LOS. (That's because the bore is below the scope.)

However, while the line-of-sight is a direct line to the target and is not affected by gravity, the bullet must be shot slightly upward because gravity will begin pulling it downward as soon as it departs the muzzle.

The bore has to be inclined relative to the LOS; there is no way to avoid it. (You do not notice the barrel inclination because you aim along the LOS not the bore itself.)

As the bullet travels upward in the trajectory arc imparted on it by the inclined barrel, it will conveniently pass through the LOS at about 25 yards if the rifle is sighted for any reasonable distance. So just boresight for 25 yards.

los

los

Well, then, why not just boresight to the range you will be zeroing for? 

Let's suppose you could distinguish the laser spot on your target in daylight at your sight-in range of, say, 200 yards. Just suppose.

If the laser spot and the line-of-sight were in coincidence at 200 yards instead of about 25 yards, the bore would not have sufficient inclination to impart the arc to compensate for gravity.

The LOS and bore (represented by the laser beam) would be nearly parallel. Neither is affected by gravity.

However, the bullet will be affected by gravity. The bullet would depart the muzzle below the LOS and continue to fall further below the LOS. The bullet would be way below the LOS at your desired sight-in distance of 200 yards.

Therefore, twenty-five yards is the best range to boresight. Besides, you do not have to walk far to hang your boresight target.

I will have an article about how to sight in a rifle scope at 25 yards. Follow my blog to update!

How to Bore Sight with Laser Boresighting

Laser boresighting is the most precise way to boresight at 25 yards. A laser boresighter will work with all types of rifle actions, including bolt actions. 

How to bore sight with a laser?

Depending on the model of laser boresighter, the laser emitter is either inserted into the chamber or into the muzzle.

Bore sighting with laser will emit a red or green laser spot directly onto the target to represent the bore. All you have to do is adjust the reticle to coincide with the laser spot.

Take fresh batteries for your laser boresighter to the shooting range. A laser boresighter is not a boresighter at all if its batteries are dead. Whether you have a laser boresighter or not, you should go to 'Print A 25-Yard Boresight Target' to select a boresight target for your rifle's caliber before you go to the rifle range. 

You can use it to visually boresight if your rifle has a bolt action or a falling block action, in a pinch if the laser boresighter batteries die, or if the day is too bright to discern a laser spot. (You should print two targets: one to post at 25 yards and one to keep at the bench for reference in case you cannot read the lines clearly on the one you posted.)

The laser spot on the boresight target is more visible on the target at 25 yards in low light than in bright daylight. In fact, you may not see the laser spot at all on a 25-yard target during bright daylight.

A green laser spot is more visible in bright daylight than a red laser spot. Preliminary laser boresighting can be done at 10 feet whether or not you will be sighting-in during bright daylight. 

Preliminary boresighting at a closer range, such as 10 feet, will not be as precise as boresighting at 25 yards, but it may help you find the laser spot on the 25-yard target later if the sunlight is bright - sort of a boresight before you boresight.

The target will not be in focus at only 10 feet distance through the scope, but you can try to laser boresight at that distance before you post a target at 25 yards if you would like.

Alternatively, if you happen to have an optical boresighter also, you can use it first then go directly to the more precise laser boresighting at 25 yards.

Be certain the rifle is not loaded. Support the rifle in a gun cradle or sight-in vise with the muzzle pointed toward a target backer about 10 feet away.

Read the instructions that are included with your laser boresighter. Install the boresighter according to its instructions. Turn the laser on. Do not look directly into the laser emitter. You should see a red or green laser spot on the backer. Post the target so the laser spot is on the circle.

How to calibrate a laser bore sighter?

Turn the scope's magnification to its lowest setting to get the widest field of view (FOV) if your scope has variable power.

If your scope is parallax adjustable, adjust it to its closest setting. View through the scope. (The target will probably be out of focus at such a close viewing distance, but you should still be able to distinguish the vertical and horizontal reference lines. Do not mess with the scope's eyepiece trying to focus the image.)

Adjust the vertical crosshair to the middle of the vertical reference line first.

Yeah, the line is probably out of focus, but do your best.

If your scope mounting system has a windage (left and right) adjustment, use that to make the vertical crosshair alignment with the reference line.

Use the internal windage adjustment dial only if your mount system does not have its own windage adjustment.

It may take several clicks to move the reticle because the click values are very small at such a close range. (The direction of the adjustments will be reversed from the label on the dial because you are attempting to be move the reticle to the reference line instead of moving the reference line to the reticle.)

Next, use the elevation dial to adjust the horizontal crosshair as close to the middle of the horizontal reference line as you can determine. The elevation adjustments will be reversed also.

That was just a rough boresight. Unless it is a bright day, you should be able to find the laser spot somewhere on your 25-yard target next for more precise laser boresighting when you view through the scope.

Claim a shooting bench with a clear view of a 25-yard target frame. Be sure the rifle is not loaded. Support the rifle with a benchrest, bipod, sight-in vise, or sandbags.

Turn the scope's magnification to the lowest setting if it has variable power.

If your scope has a parallax adjustment feature, set that to the 25 yards.

Hang a white sheet of paper or a target at 25 yards. 

Place the laser emitter into the bore at the muzzle or insert the emitter into the chamber depending on which model you have.

Turn the emitter on. 

Do not look into the laser emitter and do not point it at anyone else. (Do not fret if you cannot see the laser spot on the target at 25 yards in bright daylight. You may be able to see it when you view through the scope. That is why you did the preliminary laser boresighting at 10 feet. You can still do a visual boresight as described below to get the laser spot on target at 25-yards if you did not do a preliminary boresight.)

View through the scope and aim at the center of the target with the reticle.

You should see laser spot somewhere on or near the target if you did the preliminary boresighting at 10 feet. 

Check if the laser spot appears brighter on a white area of the target or on a black area; otherwise, ignore the markings on the target for now. (Actually, you may not see the laser spot at all on a 25-yard target during bright daylight. Reposition the target to some shade if you cannot discern laser spot).

Does the reticle coincide with the laser spot on the target at 25 yards? Probably not. Adjust the vertical crosshair first. If your scope mounting system has some sort of windage adjustment, use it to correct most of the windage deviation.

Use the scope windage dial to adjust the vertical crosshair if the mounting system does not have such a windage adjustment.

After the laser spot is aligned with the vertical crosshair, use the elevation dial to adjust the laser spot to coincide with horizontal crosshair as well.

It may take several clicks to move the laser spot to the reticle; 1/4-inch clicks at 100 yards are worth only 1/16-inch at 25 yards.

Your scope will be boresighted to the rifle bore when the reticle and laser spot coincide. 

Turn the laser boresighter off. Remove the boresighter from the bore. Reset the scales on the scope dials to the "0" index. Depending on your scope, you may have to loosen a set screw and turn a ring to index "0" or lift the knob and turn it to index "0". (Refer to the scope instructions.)

Now I think you know how to sight in a scope with a laser bore sighter. Have any questions, do not hesitate to ask me in the comment section!

How to Bore Sight with Visual Boresighting

If you do not have a collimator or a laser boresighter (or if the batteries of your laser boresighter are dead or the day is too bright to laser boresight), you can visually boresight. That is, if your rifle has a bolt action or a falling block action. (If your rifle does not have a bolt action or a falling block action, you will need an optical boresighter or a laser boresighter.) 

Visual boresighting is not as precise as optical or laser boresighting, but it is better than shooting bullets and wondering if any will even hit the target let alone the bullseye.

Remove the bolt from your bolt-action rifle or drop the breechblock if it is a falling block rifle.

You must have an unobstructed view of the target through the bore if visual boresight is going to work. 

Post a boresight target at the 25-yard. Turn the magnification down to its lowest setting to increase the FOV if your scope has variable power. 

Set the parallax adjustment to 25 yards if your scope has such a adjustment.

Support the rifle on a benchrest, bipod, or sandbags pointed at the target.

Position your aiming eye behind the heel of the buttstock so you can view the target through the receiver and bore.

View the target through the bore

View the target through the bore

The FOV through the bore is quite small so you may have to move the rifle a bit to find the target.

After you finally locate the target through the bore, stabilize the rifle with sandbags so the bore continues to point at the target when you let go. 

Without disturbing the rifle, turn the windage dial then the elevation dial to align the reticle with the center of the target. 

Since you are trying to move the reticle to align with the bore instead of the bore to the reticle, the click adjustments will work backward.

Remember, each 1/4-inch click at 100 yards is worth only 1/16-inch at 25 yards. It will take several clicks to move the reticle a only a small distance.

If your scope mounting system has a windage adjustment, use it to make most of the windage adjustment.

Recheck the bore alignment to the target if you bump the rifle while adjusting the scope.

The scope is boresighted when the target is still centered in the bore while the reticle is centered on the target. 

Visual boresighting can be tedious. Visual boresighting is obviously less precise than laser boresighting, but it is better than not boresighting at all.

To save time and to save ammunition are two good reasons to boresight. There is another good reason to boresight: to keep yourself from looking like a fool. 

You do not want to be the only shooter at the range scratching your head wondering just how the heck you missed that whole darn sight-in target with your first few shots while all the other shooters are pointing at you and snickering.

Yes, boresighting is an extra step in the sighting-in process. However, it is not difficult to do and it will make sighting-in much easier overall. 

Maybe you will get lucky and hit your sight-in target with your first shot without boresighting. Maybe. Don't count on it. Better just boresight.

I will write an article about how to sight in a rifle scope without a boresighter soon. Please wait!

Coming soon

  • How to use a laser bore sighter on a pistol
  • How to boresight a semi auto rifle
  • How to sight in a rifle scope at 50 yards
  • How to zero an air rifle scope
  • How to boresight an m4
  • How to bore sight ar-15 scope
  • How to boresight a ruger 10/22
  • How to bore sighter for 22 rifle
  • How to boresight a muzzleloader
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