DIY

Best Practices for Mounting Optics on Rifles

Rifle Optic Mounting

When looking over the used rack at the gun shop, it isn’t unusual to find a number of scope-mounted rifles. About half have improperly mounted scopes.

Some are cocked sideways, the adjustment knobs are in the wrong place, or the scope isn’t properly tightened. Sometimes the scope is overtightened, which may damage the scope.

I have even found a scope touching the rifle barrel. I think sometimes that the owner has kept his nice scope and hastily placed a cheap scope in the mount before trading.

But then I sometimes find a rifle with a Nikon or Leupold scope. There are many shooters that purchase inexpensive package rifles with the scope mounted and bore-sighted.

But if you purchase a more expensive rifle scope you will need to mount it yourself. While a gunsmith may do the job, this gets expensive.

No matter how good the rifle scope, if the optics aren’t properly mounted and affixed to the receiver, then the scope isn’t going to do the job it is intended for.

Let’s go over some best practices for rifle optic mounting.

Bolt-Action Rifle with Scope
This is a high mount that would suit some, but not all shooters.

Pick the Right Scope

First, choose the scope. There are many good-quality rifle scopes, so choose the one that suits your needs. Use a chart to choose the proper rings and mounts.

(A tip: the scope should be mounted as low as possible. Gone are the days when stocks were designed for iron sights.)

The modern rifle will help place the eye in the proper location for fast, accurate shooting. If the objective lens is large, you may have to compromise a bit on the mounts.

Eye relief is important. Eye relief is simply the distance from the eye to the scope. Eye relief will decrease from low to high power settings.

So, the eye relief should be set so that the scope is useful either at high or low magnification settings.

Another caution— if the rifle is chambered for a more powerful cartridge, beginning with the .308 and certainly the .300 Magnum, be certain that the scope isn’t set where it will whack your brow in recoil.

The eye should be able to quickly pick up that centered circle of light for aiming. I find about three inches of eye relief works for most shooters.

To properly focus the ocular lens, commonly called the eyepiece, simply take an aim with a triple-checked, unloaded rifle at a solid, colored target 10 to 20 yards away.

Turn the eyepiece until the sight picture is clear and in focus.

Shooting Rifle with Scope
Be certain the scope has enough eye relief to avoid the scope jolting the brow during recoil.

Create a Secure Foundation

Scope bases and mounts are important. Modern Picatinny rails make mounting simpler. But bolt-action rifles, in particular, use individual mounts on the receiver bridge.

The scope bases must be securely mounted to the receiver. The distance that separates the mounts must correspond to the space between the rings on the scope.

When mounting the bases, I tighten each screw a bit, then the other screw, and so on. I don’t tighten one too much at first, I even things out.

As you work the screws, the base or mount will be tight and secure to the receiver. While it seems odd, occasionally you will run across screws that are too long, especially in used guns with hasty mounting.

After the bases are properly mounted, use Loctite to be certain they are secure. If you overtighten, the threads may be stripped.

Bad Scope Mounting
In this illustration, note the scope is touching the rifle barrel— bad harmonics!

Make Sure Everything’s Aligned

As you move to mounting the rings, mounting them evenly and properly centered is important.

A professional may use a special tool but the average shooter may be able to mount the rings with care.

Slip the rings in place and be certain that there are no burrs in the rings. Occasionally, it is necessary to lightly sand and polish the rings.

I have taped the inside of rings to ensure the rings don’t scratch the scope tube.  There cannot be any binding of the rings. The scope tube may even be damaged.

The ring edges are especially a point of interest. Be certain the rings are properly lined on the scope body.

While it is ok to get the rings tightened to an extent, be certain that you have enough of a loose fit to allow the scope to move a bit as you adjust eye relief.

It is surprisingly difficult to get the reticle perfectly centered. This is the single most common demerit I have observed in used rifles and rifle scopes in shops.

They are traded in like this. When the rifle is quickly mounted and the stock solid in the shoulder, the eye should naturally go to the eyepiece and find the reticle.

When this alignment is properly set up, the rings should be tightened slowly and carefully, making certain not to lose the proper adjustment.

AR with Scope
This TRUGLO optic may be a bit forward for some of us, but if the scope is removed, backup sights are instantly available.

Move On to Bore Sighting

To sight the rifle in, it is sometimes beneficial to set the rifle in a rest and then remove the bolt.

Look through the bore and then you will find a spot on the wall or perhaps out the back yard window, and then adjust the scope to set the reticle on this target.

The windage turret adjustment moves the crosshairs right or left, the elevation adjustment moves the reticle up and down. This is called bore sighting.

There are devices called collimators that use a spud of caliber diameter to mount in the barrel. The reticle is adjusted against an aiming point in the collimator.

These are neat tools and so are laser bore sighters. I use the method of boxing in the shots on the target.

I begin firing at 25 yards. If the rifle has been properly bore-sighted, the rifle will group nicely on paper. I fired a shot and then I move the adjustment turrets.

I normally work only one turret at a time. If the scope is properly mounted, it isn’t difficult to get in line quickly.

I move the turrets the specified amount—usually a click equals a quarter inch—and get in line.

Once a single bullet hits in the proper spot, I move to the next option, usually beginning with windage and then moving to elevation.

I usually set the point of impact, versus point of aim, for two inches high at 25 yards.

Finish and Fine Tune

Despite advanced apps, formulas and electronic and mathematical wisdom, I find that only actual firing is reliable for fine-tuning the point of impact.

I like to set a hunting rifle for an inch to two inches high at 100 yards, achieving a shoot flat hold to 125 yards. It depends on the use the rifle will be put to.

A wild boar rifle might be used at fifty yards, a deer rifle at one-hundred to two-hundred yards, and a varmint rifle, well, the distance at which you can see the critter.

Follow these simple rules, enjoy your range time and get your optics sighted correctly.

TruGlo Scope
TruGlo scopes offer turrets that are easy to adjust.

Do you have any favorite scopes or mounting options? Let us know in the comments below!

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (12)

  1. Doing a good job for nearly anything should involve buying and using the proper tools. The easiest way to properly mount a scope on a rifle is to buy a mounting kit that includes an inch-pound torque wrench, leveling bubbles, and lapping bars, then following the directions. Trying to guess on issues like levels, screw tightening, ring to scope tube fit, and others is close to impossible. A one-time purchase of the right tools will provide a lifetime of use for not only yourself, but your friends as well. Unless you hunt in your back yard, the cost of a mounting kit will be substantially less than a single hunt, and prevent a lot of grief later on. The idea of starting the sight-in process at 25 yards is spot-on. It should not take more than three or four shots to zero a scope well enough to allow it to be fine-tuned at any distance desired.

  2. When I mount a scope, I have a certain routine I go through with ALL my mounting procedures.

    I made a fixture for mounting the upper assy in, which I also use for firearm maintenance and bore sighting. [Not a shooting rest.]

    I will square the upper assy in the fixture, leveling the upper with the fixture, lock it down, locate the scope mount on the upper, establishing the mount location based on eye relief, rear sight location clearance (if needed) and take measurements to be sure the mount is centered over the barrel and shroud.

    Then I use the shaft from my Wheeler scope kit and check the alignment of the shaft to the barrel shroud both for alignment to the bore and parallel to the bore, again taking measurements.

    Then I lay the scope in the rings just loose enough to move it.

    This is where I probably differ from some peoples mounting regime.

    I use levels to square the scope and upper BUT I also set up a plumb bob about ten feet away and line the vertical crosshair with it, making sure that my levels all correspond.

    After gradually tightening the scope in the mount, making sure all the levels correspond to each other and the vertical crosshair stays parallel to the plumb Bob, I will then bore sight the assy.

  3. I finally purchased a wheeler mount kit with 1″ and 30mm ring aligment and lapping tubes. This kit makes a world of difference in the ease of getting scope mounted, dealing with imperfect mating of rings and scope, and leveling the reticle. Add the loctite while scewing down alternating screws (as you mentioned) and the thing won’t move on you. I carry blue loctite in all my cleaning kits, range bag etc. Pretty much anything and everything that needs to stay put gets it!

  4. I have found what works best for me when mounting scopes to full picatinny rails like the ones found on AR’s is to mount the one piece or two piece scope base on to a 1/2 ” 12 or 13 slot riser that has thumb knobs with slots cut in which allows one to use a quarter to install, move or remove riser on picatinny rail quickly and easily without the need of allen wrench. This method guarantees maintaining Zero and allows shooter to switch from scope to iron sights/flip up sights with very little effort, and if one found himself in a fire fight and wanted or needed to remove scope the riser helps facilitate this much better than having to pull out an allen wrench for removal of scope in a time of need. HELPS KEEP YOU IN THE FIGHT!!!!

  5. Rifle sidly mounted, unmovable, perfectly leveled, Height I’m puzzle same as height of a mounted targets bull.with perfect centered horizontal and verticle intersecting lines with crossing point highlighted by 1″-2″ square.
    Used to log and fall timber and still have very strong hands but cannot feel how much torque I am applying , so I use quality electronic readout t orque ,screwdriver-wrench on the best mounts and rings i can afford.
    Also use micrometer to insure correct diameter and concentricity before monting rings; have found even most highly touted brands rings that needed shiming, with burrs and beveled and tapered inner diameters, so that when I mount permanent I use real locktite.
    I do not tighten for long-time until after I have found perfectt eye relief for me no one else.
    When doing others want them to hold for their physique.
    Am picky for just a hunting scope setting but one from time when amo was costly, we could even buy partial box from country store, from 22cal bees to 30/06, so we made each shot count.
    And being a brush woods, swamps or corn field in those days no one, except New York Swells and Boston Beaners shot at deer, moose or Bear at over 200 yards, even those with early scopes.
    Learned lesson years ago that cheapy scopes to best made have to be mounted right.
    Now a days use a laser bore sighter, and pretty well know at 25 foot where to Zero , height for different rounds that zero in at 200 on paper, my preference for each caliber that is 200 max and under and those capable for over.

  6. I would recommend using the ballistics tables in the back of the Sierra Bullets Reloading Manual, 2nd edition (and maybe subsequent versions). It covers three applications of sighting in rifles…for varmint, larger game and competition shooting. For bolt action rifles I use the bore sight method but keep the point of aim at the target spot centered in the bore twenty five yards distant. Then firing a round from a solid rest, adjust windage and elevation until crosshairs and bullet strike are aligned. Then fine tune using the above mentioned table(s) for the particular caliber/muzzle velocity/application. After all is accomplished there is only one other step…practice, practice practice… from all shooting positions you might expect in the field or in competition.
    Regards

  7. Use a torque screwdriver like the FAT. Go to your local hardware store and get a couple of bubble levels, just the vial part, put one on the receiver and one on the cap of the scope to check level at the same time.
    Personally I dont mount optics to the handguard of my AR rifles. I use offset or 45 degree backup sights with my scopes. With red dot sight then I will use flip up sights.

  8. I have a Marlin 30-30 lever action that I would like to mount a scope on. It will need to be drilled and tapped. I would like to do it myself. Any advice on centering or mount to use ? Thanks.

  9. Sight your AR in at 50 yds. It will impact about 1 1/2 in. high at 100 yds. and drop right back into the 10 ring at 200 yds. Remember your scope is above the bore and the round has to climb to the impact what ever yardage your zero is. At 25 yds.impact should be below point of aim. Try one inch low and then move to your desired zero range and fine tune from there. Make sure there is NO cant in the scope so your impact stays centered as you adjust for different distance.

  10. Always a good idea to learn the trajectory of the round you are using before you begin set up.
    Many people simply ” zero it at 100 yards ” regardless.
    The trajectory and intended use will help you determine the best distance to zero the scope.

  11. I love these topics and my choice for scope mounts and rings goes to DNZ. I was introduced to them a few months ago, and the one piece base/ring when tightened correctly is rock solid. I hope someone reads this and decides to go with these mounts!

Your email address will not be published. Required fields are marked *

Time limit exceeded. Please click the reload button and complete the captcha once again.

Your discussions, feedback and comments are welcome here as long as they are relevant and insightful. Please be respectful of others. We reserve the right to edit as appropriate, delete profane, harassing, abusive and spam comments or posts, and block repeat offenders. All comments are held for moderation and will appear after approval.