This guide on Mounting a Rifle Scope was written by our resident Director of Product Intelligence, Steve Ledin. It originally appeared in conjunction with our Selecting Scope Mounts, Rings and Bases on Steve's blog Riflescopeblog.com. If you're interested in learning even more about all things firearms and hunting, be sure to check out Steve's blog, and read on to learn what you need to know to mount your scope right.
Mounting Your Rifle Scope
If you choose to mount a riflescope yourself you will need a few things first. A gun vise of some kind and a clean, well lit area. Remove any filler screws in the top of your receiver with a properly fitted screwdriver. Degrease the holes. This of course does not apply to grooved receivers or integral Weaver/Picatinny bases. Degrease all mount parts, then reapply a light coat of oil to the top of the receiver and the bottoms of the bases or rings. Check the instructions for your particular mounting system. Some manufacturers that use Torx screws suggest a light coat of oil on the screw threads. I normally use Loctite on all base screws. Never Loctite ring screws. Always apply to the screws, not in the threaded holes. Some bases will have screws of different lengths. Check them first visually. Make sure the screws are in the correct places. Screw threads should protrude about the same amount from the underside of the bases. Putting too-short screws in the wrong places can result in a scope being torn off by recoil or handling, and screws that are too long can bind a bolt or result in a loose base. Install the bases using Loctite or oil, depending on what the manufacturer suggests. A tiny dab of fingernail polish works well when Loctite is not available. Tighten securely.
Next, install the bottom half of the rings onto the bases. If you have a Weaver or Picatinny system you may tighten them securely with a properly sized screwdriver or wrench. If you have a Leupold turn-in style you will need to assemble the top half of the ring onto the bottom ring, place it in the base, and use a wooden dowel or non-marring screwdriver handle to turn the ring 90 degrees. This is a press fit and cannot be done by hand. Do not remove the factory applied grease on the mating parts. Every time a Leupold system is installed it gets a little looser. Reapply grease if needed. A Leupold ring wrench is worth its weight in gold for installing rings.
If using a dual dovetail system, repeat this procedure for the rear ring. The adjustable rear base on a standard Leupold system has two opposing screws that allow for significant windage adjustments. Center the ring onto the base by eye and snug the opposing screws.
This is the time to use a scope ring alignment tool if you have one. Those sold by Wheeler Engineering are excellent, and prevent damaged scope tubes caused by misaligned rings. These tools are two piece 1" or 30mm rods. Each one has a pointed end. Install the alignment tool between the ring halves and move the front and rear rings using the alignment tool until the pointed tips of the tool are almost touching.
Remove the top halves of the rings and place your scope in the bottom ring halves. The scope should fall to the bottom of both rings. You can lightly install your top ring halves.
Remove the bolt of your rifle if possible and look through the bore at a target placed at least 25 yards away and adjust your scope so your crosshairs are pointing at the same place you see when looking through your barrel, or use a boresighter of any kind. Results are about the same with any type of boresighting. I prefer a magnetic boresighter such as the Leupold, which does not require specific arbors or lasers, and a target set some distance away is not needed.
Remember, boresighting will simply get your shots on paper at shorter distances so you can sight in by actually shooting at a certain distance with a certain load. No boresighter can sight in a gun. Period.
If you can easily adjust your scope when boresighting to approximate center without significant manipulation of the windage and elevation knobs on your scope you are ready for the next step. If your windage is off a lot and you have standard Leupold type bases with windage screws, take your scope back out before you move the bases accordingly so you don't misalign your rings and damage your scope. Move the rear base and realign both rings with your alignment tool or place your scope back in the bottom ring halves and ensure the scope drops to the bottom again. Lightly install the top halves of your rings and check the boresight again. With dual dovetail systems you have no option for base adjustments, so if your adjustments are at their maximum, switch to a base with windage screws. If you have a Weaver/Picatinny system and your windage is off, some manufacturers like Millett offer rings that are windage adjustable. If elevation is an issue with any system you may have to place a shim under your front or rear base, or get a base with built-in elevation.
If you don't have a boresight or alignment tool just do the best you can by eye. You can use a 1" or 30mm bar or an old scope that you won't mind a scratch or two on to see if it falls to the bottom of the rings. I still sometimes use a piece of an old Harley handlebar that measures .9997 and is perfect.
If your boresight looks good you may now lap your rings if you like. Lapping polishes the inside of your rings. Lapping tools are available from Wheeler Engineering and they not only ensure maximum scope to scope ring contact, but remove any sharp edges on rings that can scratch scopes. Instructions are provided with these lapping tools. The Tipton gun vises and the Wheeler Engineering screwdrivers, alignment tools, and lapping bars are an important part of any firearm workspace and are inexpensive investments that will last a lifetime.
If you have lapped your rings, take care to remove all traces of the abrasive lapping compound with a solvent, then degrease with a moistened patch. Place your scope in the bottom half of your rings and loosely install the top ring halves. With your scope at its highest magnification, aim the scope at a bare wall some distance away or at the sky, and adjust the eye relief. To do this, move the scope gently fore and aft until you get the maximum distance the scope can be from your eye and still give you a full sight picture. At lower magnification you generally have more eye relief available, so remember to set the placement of your scope when it's at its highest magnification.
This is also the time to level your crosshairs. Again, Wheeler Engineering sells a neat leveling product that rests on your gun and your scope that takes the guesswork out of this procedure. Adjusting the crosshairs by eye is loads of fun. You'll often have to loosen your ring screws to re-level several times until you're satisfied that the reticle is straight. Tightening your ring screws also moves your scope slightly one way or another. Tighten the top half of your ring screws evenly from one side to the other, just a bit at a time and always from one side to the other, trying to keep the gap between the rings even. There will be a gap. Tighten your ring screws securely, but don't try to tighten the screws enough to close this gap.
With your scope now securely mounted, check the function of your gun to make sure the action is not bound by too-long base screws and that the ocular bell does not interfere with the manipulation of your bolt on a bolt action rifle.
Boresight your gun and shoot! Check the tightness of your ring screws occasionally. Have fun!
Steven K. Ledin
OpticsPlanet Director of Product Intelligence