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Scope Mounting: How to Mount a Rifle Scope

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Remington 700
Remington 700 in .308 with custom shortened barrel. Photo: Terry Nelson

Rifle Scope Mounting:

How to mount a rifle scope —

We will start from scratch here. A brand new remington 700 bolt action rifle, two piece windage adjustable scope bases, scope rings and a Leupold 3-9 scope–a fairly common hunting rig. Now let’s mount the scope on the rifle the right way to achieve the rifle’s full accuracy potential.

If you follow this rifle-scope mounting procedure exactly it will be impossible to cant the rifle scope therefore adding the potential for better rifle accuracy.

1. Mount the rifle in a padded vise as far away from a wall opposing the muzzle end of the rifle, the farther away the better.

2. Attach the scope mount base to the rifle securely.

3. Now take a level and lay it on the base horizontal to the rifle bore. Level the rig out in the vise and lock it down.
(See Image Below)

4. Attach the scope rings, make sure the scope will lay down into the rings without them moving when you go to tighten the scope into the rings.

5. Now take the scope and put it between 2 v blocks and spin the scope watching the crosshairs for wobble, adjust the scope to insure there is no wobble in the crosshairs, this is critical to your long range rifle accuracy.

6. Check to make sure that your rig is still level in the vise and then set the scope in the rings.

7. On the opposing wall away from the rifle muzzle draw a vertical and horizontal line, again using a level to insure that the line is plumb vertically and level horizontally. It should look like a plus sign.
(See Image Below)

8. Remove the bolt from the rifle, looking through the rifle’s bore, center the plus sign in it. If you can’t remove the bolt use a laser chamber bore sight only.

9. Do not use the windage screws on the scope for this procedure. Align the vertical post in the scope with the vertical line on the wall using only the windage screws on the scope base and tighten down the scope rings, make sure that all stay level and plumb vertically and horizontally.

10. If you have done everything correctly, you have just mounted the scope to all the exact tolerances that have been machined into all the scope mount components. Everything is to its true and exact mechanical center point. Your rifle’s scope is now properly mounted and is range ready for an Accurate Sight-In.

Measuring Mounted Rifle Scope Height:

A good stainless steel 6″ dial caliper will deliver unfailing .001″ accuracy for checking outside and height measurements and is the precise tool needed for this job.

Note: This works for almost all rifles regardless of action type.


Step 1. Measure the rifle barrel diameter where it attaches to the rifles action under the scope and divide it in half.

Step 2. Measure the scope diameter directly over-top of where you got barrel diameter measurement and divide it in half.

Step 3. Measure the distance from the top of the rifle barrel to the bottom of the scope on the rifle where you measured both diameters.

Step 4. Add the numbers in steps 1-3 — Step 1. + Step 2. + Step 3. = Step 5.

Step 5. The answer is rifle bore centerline to scope centerline distance or “Scope Mount Height.”

Leupold Mark 5 scope: sweet for the long range

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scoped ar-15
A Savage MSR Recon plus a Leupold Mark 5. This powerful scope made the little AR easily reach small targets at 600 yards.

Leupold has long been recognized as a producer of quality hunting scopes. Until recently, I was unacquainted with the company’s offerings of tactical riflescopes. In a range test of their new Mark 5 3.6-18 x 44mm scope, I found some great features that are competitive and, in some ways, better than comparable models.

Using a 20 MOA rail mount provided by Leupold, the big scope was installed on a Savage MSR Recon, an AR-15 with a 16-inch barrel. The Mark 5’s 33mm tube and housing for the 44mm objective lens cleared the Picatinny rail with room to spare. A 7075 aluminum housing makes this scope a light 26 ounces for its size; the Recon was perfectly manageable with it.

Leupold rifle scope
The big 44mm objective lens, with a 35mm tube in 7075 aluminum housing, makes a lightweight but serious scope.

Approximate zeroing was first done at 25 yards, and having confirmed that rounds were landing on paper, final zeroing was done for 100 yards. Windage was near perfect out of the box. Considering the 20 MOA base and rather diminutive caliber, it was little surprise that elevation required substantial adjustment. In fact, it provided an opportunity to operate one of the scope’s modern features—zero stop adjustment knobs.

zero stop
Zero-stop turrets are a great asset. The windage knob comes with a protective cap.

For those unacquainted, zero stop dials allow for the windage/elevation knobs’ dials to read -0- in sync with the shooter’s chosen actual zero. This trait of quality, modern tactical scopes makes going back to the last known zero faster and easier, and eliminates a lot of guesswork in the field—assuming a body remembers to return to true zero after making more than a full revolution.

Operating the elevation turret is a joy. It locks down so it can’t be inadvertently moved, but is easily pulled up to rotate. The windage turret is covered by a screw-on cap, a mixed blessing. The cap’s matte surface hides the setup’s white dials, making it less visible in a tactical or hunting situation. But adjustment means unscrewing and keeping track of the cap. Since windage in the field changes dynamically with wind and is normally a hold, not a dialed-in change, the cap is good protection. The picky side of me doesn’t like the mismatched look, but looks really don’t matter!

The Mark 5 as sampled, with the Tremor 3 reticle, has mil-to-mil adjustments and reading, which is to say both the reticle hash marks and windage/elevation click values are set to metric, AKA milliradian, mRAD, or mil, increments. Each smooth click on the elevation knob equals a 0.1 mil adjustment at 100 meters. This is another trait of today’s advanced long-range riflescopes, and much easier to use than many made during the transition of the long-range scope market, in which a milling reticle and minute of angle (MOA) dials were combined on the same scope.

While it’s an intellectual leap to move from the traditional American MOA system to mRAD, it’s even more challenging to keep the hands operating MOA dials while the eyes read mils.

Speaking of the reticle, the Tremor 3 model on the sample scope is now among my favorite “milling” reticles. It’s set on the first focal plane, another advantage for the shooter as the relationship of hash marks to target doesn’t need to change to stay accurate as magnification is altered. Additionally, first focal plane reticles are easier to “read” on target at long distances and/or high magnification as compared to more traditional second focal plane reticles. Not every reticle in the Mark 5 series is on the first focal plane.

reticle
An earnest but imperfect attempt to show the Tremor 3 reticle at 12x. This reticle is the perfect union of precision and intuitive features.

The Tremor 3, a Horus design, is both richly detailed and easy to read at distance. Instead of just hash marks, its X axis has bubble-shaped gradations too, which largely eliminate the need to mentally count “one-two-three-“ and so on when trying to locate a hold, for example 2.5 mils left. Using the Tremor 3 is as intuitive as current technology can make a reticle. It’s as useful in and detailed in terms of precision as the Horus H9, also available on the Mark 5, but faster to use. That’s a huge advantage in the field where targets don’t stand still forever.

A more traditional crosshair reticle called the TMR, the Horus H9, and another “Christmas tree”-like milling reticle, the FFP-CH, are all options on the Mark 5. An illuminated version of the TMR is also an option. Although I didn’t test the others, it’d be hard to persuade me away from the Tremor 3 after this test—it offers the best features of them all for precision rifle work, save for illumination.

The glass on this scope is clear and without perceptible flaws, as we’d expect from Leupold. A side parallax adjustment is included; at 600 yards I could perceive little difference when moving it off the infinity setting, so left it there.

Throw lever
3.6-18x makes for powerful magnification. A throw lever makes it easy and fast to change magnification while staying on target.

Within 15 minutes of installing the Leupold Mark 5, the little Savage Recon was hitting a 12-inch gong with near-boring reliability, with 55 grain FMJ, in a variable 8- to 12 mph wind. The Mark 5 enabled this AR to perform at a high level with average ammunition, in a short time. On the long-range precision rifle this scope is built to match, paired with only a basic understanding of ballistics, incredible results are within reach for just about any shooter.

The Mark 5 is priced in the ballpark of other precision riflescopes of this type, with the advantage of a wide range of reticle choices. The sample scope, is priced at $2,729.99. The bottom of the price range features the non-illuminated TMR reticle, at $2,399.99, and the same reticle, in the illuminated version, is represented at the top, $2,989.99. Actual retail prices will vary, like this one found on Amazon for under $1,800.

How to Sight In A Rifle

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Rifle Sights And Bullet Trajectory:

1. This first thing to know when sighting in a rifle is that all rifle sighting systems give you a point of aim on any target.
2. The second thing to know when sighting in a rifle is that all rifle sighting systems compensate bullet drop.
3. The third thing to know when sighting in a rifle is that a bullet constantly drops once leaving the rifle barrel, the arc that it drops in is the bullet trajectory.

Rifle Sight-In Procedure:

Step 1: Place your target at exactly 50 yards down-range, (quality rangefinders) offer a good quick reference if in doubt about distance from target, be sure that your down-range area is clear and safe to shoot. Wear ear and eye protection while shooting. Always use a target that you can clearly see with your sight system, preferably with 1″ graduation grid marks.

Step 2: Go to your shooting position, load your rifle with one shell at a time as you will need to shoot at least 3 rounds of ammunition for a group to assure everything is accurate and tight on the rifle. Line up your sights correctly and fire one accurate round. Clear your spent rifle cartridge case and wait approximately 1 minute to cool the rifle barrel. Repeat this procedure for three rounds of ammo.

Step 3: Make an exact measurement from the center of your group to the center of your target and make your windage and elevation adjustments accordingly, if you need to go left or right and you have windage adjustable scope bases, use the windage screws on the base, rule of thumb for windage adjustment, if your bullet impact is to the left side of target center loosen the right rear windage screw on the base and tighten the windage screw on the left rear side of the base.

Step 4: Fire three more rounds to confirm your setting, if all is well and you have centered your group move on to step 5. If you are not satisfied with the accuracy of your ammunition at this point go no further until you have the groups you are happy with.

Step 5: You have now established a 50 yard reference zero point, next you have to do bullet trajectory plotting to see if this zero point is what you want for a true rifle zero. Bullet trajectory plotting is nothing more than shooting at targets at various distances and recording the bullets impact at those distances.
Hunting Rifle Sight-In:
External Ballistics:
External ballistics pertains to bullet velocity, energy and trajectory down-range. Bullet trajectory is the flight path of the bullet relative to some known and fixed points.Bullet Trajectory And Sighting Plane:
1. Point blank range when sighting in a rifle is the first point at which the line of sight intersects with the bullets path in the bullet’ s trajectory.
2. Mid-range rise when sighting in a rifle is the highest point in the bullets trajectory between the point blank range and true zero.
3. True zero when sighting in a rifle is the second point at which the line of sight intersects with the bullets path in the bullets trajectory.
4. Maximum point blank range when sighting in a rifle is the height of the mid-range rise and the bullet drop beyond true zero, both are equal in measure.

More in depth rifle sight in:


Larger Image View Rifle Sight Height And Bullet Trajectory:
To properly sight-in a hunting rifle a person needs to know a little bit about their scope mount height of their rifle as this affects the sight plane that intersects with the bullet’s trajectory.

Rifle Sight Height to Bore Center Line:
Open Sights = 1 inch sight height.

Rifle Scope Center Line to Bore Center Line:
Low Scope Mount And Rings = 1.5 inch sight height.
Medium Scope Mount And Rings = 1.8 inch sight height.
High Scope Mount And Rings = 2.0 inch sight height.

Rifle Barrel Length, Bullet Velocity And Energy:
Bullet velocity readings are generally taken from a rifle barrel length of 24 inches and using the following formula the bullets energy is determined; velocity x velocity x bullet weight = _ divided by 450,340 = bullet kinetic energy in foot pounds.
If your rifle barrel length is not 24 inches then you have to recalculate the bullet velocity and bullet energy.
Rifle Barrel Length Shorter Than 24 Inch You Subtract Velocity.
Rifle Barrel Length Longer Than 24 Inch You Add Velocity.
2,500 to 3,000 feet per second advertised velocity, adjust at 20 feet per second per inch from standard of 24 inch rifle barrel.
3,000 to 3,500 feet per second advertised velocity, adjust at 30 feet per second per inch from standard of 24 inch rifle barrel.
3,500 to 4,000 feet per second advertised velocity, adjust at 40 feet per second per inch from standard of 24 inch rifle barrel.

Bullet Ballistic Coefficient:
The bullet ballistic coefficient, higher B.C.s mean flatter trajectories and higher retained energy down-range on target. A ballistic coefficient is the measure of a bullet’s relative ability to overcome air resistance. Each bullet is assigned a numerical value expressing this efficiency. Ballistic coefficient calculations combine both shape and sectional density factors.

Bullet Sectional Density:
Bullet sectional density is a mathematical factor expressing the relationship between the weight of the bullet and its cross-sectional area. Sectional density best describes a bullet’s length as to its diameter, the higher the number, the longer the bullet. Generally speaking, longer bullet’s of a given diameter (high S.D.) will penetrate deeper than will shorter bullet’s of the same given diamter (low S.D.). Having said that, bullet construction ultimately determines its usage for hunting, always follow recommendations by the manufacturer.

Bullet Energy:
Before the bullet is down-range and on target, you have to know whether the bullet will have enough energy retention to cleanly harvest the animal. A bullet’s kinetic energy is measured in foot pounds, and this is a proxy for what’s generally termed stopping-power. The higher a bullet’s energy at the point of impact, the greater its stopping-power.

Bullet Impact Zone:
Just as important is the size of target that a game animal that your hunting presents to you, typically standing broadside, exposing heart and lung area.

Hunting Rifle Sight-In Procedure:
1. At exactly 50 yards put up a target that you can clearly see with your sight system.

A. For a air-rifle of reasonable power, 50 yards will most likely be the furthest maximum point blank range in the trajectory path for sighting in purposes.
B. For a rimfire rifle, 50 yards will most likely be the true zero point in the trajectory path for sighting in purposes.
C. For a muzzleloading rifle, 50 yards will most likely be the mid range rise in the trajectory path for sighting in purposes.
D. For a centerfire rifle, 50 yards will most likely be the point blank range in the trajectory path for sighting in purposes.

2. Now with your rifle properly rested on a rifle rest on top of a solid shooting bench, slowly and methodically fire three precise rounds.

3. Make an exact measurement from the center of your group to the center of your target make your windage adjustment accordingly, if you need to go left or right and you have windage adjustable scope bases, use the windage screws on the base, not the scope, rule of thumb for windage adjustment, if your bullet impact is to the left side of target loosen the right rear windage screw on the base and tighten the windage screw on the left rear side of the base.

4. Fire three more rounds to confirm your setting, if all is well and you have centered your group move on to step 5. If you are not satisfied with the accuracy of your ammunition at this point go no further until you have the ammunition you are happy with.

5. Depending on your rifle scope this is all you will be able to accurately do for this range outing, there are a lot of rifle scopes that do not like windage and elevation adjustments all at the same time. Any attempt to keep shooting with one of these scopes will only waste ammo and aggravate you to the point of despair.

6. Establishing a reference zero.
A. Low powered air-rifles and small .22 rimfires, at exactly 50 yards zero your rifle.
B. More powerful rimfires move out to exactly 75 yards and zero your rifle.
C. 30/30 trajectory class centerfire rifles and muzzleloading rifles move out to exactly 100 yards and zero your rifle.
D. High powered rifles move out to 100 yards and make sure your rifle is still center and a little high and then move on out to 200 yards and zero your rifle.

7. Trajectory plotting your rifle and ammunition combination for proper sight in.
Class a and b rifles take your target and move it closer to you, firing 3 shot groups in 10 yard increments, mark the range on the target at each shot group.
Class c and d rifles take your target and move it closer to you, firing 3 shot groups in 25 yard increments, mark the range on the target at each shot group.
A. Continue moving the target closer to you until one group of shots emerges as the highest, this is confirmed when the next target move closer to you the grouping is lower.
B. Congratulations riflemen at this point of the rifle sighting in procedure you have now established a true zero point and more importantly you have found the mid-range rise for your rifle, scope mounting, and ammunition selection.
C. Now measure the center of your highest group on your target to your zero point, this is your true mid-range rise.
D. Is this acceptable, or does it need to be adjusted for more or less rise.
D. part 1. If the mid-range rise is to much, class a & b rifles move your target 10 yards closer, class c & d rifles move your target 25 yards closer to you from your original zero yardage and re-zero your rifle. Then repeat step 7 of the rifle sight-in procedure again.
D. part 2. If the mid-range rise is not enough, class a & b rifles move your target 10 yards further, class c & d rifles move your target 25 yards further from your original zero yardage and re-zero your rifle. Then repeat step 7 of the rifle sight-in procedure again.
Note: Repeat this procedure till you have exactly what you want.

8. Establishing your rifles maximum point blank range.
Now that you have established your mid-range rise and your true zero, it’s time for the final step in properly sighting in your rifle (M.P.B.R.).
Class a and b rifles take your target and move it from your true zero point further from you, firing 3 shot groups in 10 yard increments, mark the range on the target at each shot group.
Class c and d rifles take your target and move it from your true zero point further from you, firing 3 shot groups in 25 yard increments, mark the range on the target at each shot group.
A. Continue moving the target further from you until one group of shots emerges as the same distance low as your mid-range high.
Note: Example 2″ high, 2″ low.
B. At this point of the rifle sighting in procedure you have now established a true zero point, you have found the mid-range rise and you have found your true maximum point blank range for your rifle, scope mounting, and ammunition selection.
Your Rifle Is Now Properly Sighted-In.
This is the only way to properly sight in a hunting rifle.