Scope Mounting

Most rifle scopes get mounted the same way shanties get built: fast, crooked and defended later with the phrase “good ’nuff.” The rifle goes on the kitchen table, the rings get snugged by feel, the reticle looks straight enough if you squint, and the whole thing goes downrange with optimism doing all the heavy lifting. Occasionally, it works. Often it doesn’t. When it doesn’t, the shooter starts chasing ghosts — bad ammo, bad barrel, bad scope, bad advice — while never suspecting the crime scene sitting quietly right on top of the receiver.

If your scope is misaligned, loose and/or damaged, what you’re doing is essentially guessing instead of using a precision aiming device. Even if things are tight, but the scope is “almost” level, your dialed-in adjustments are walking off-axis. If you stack loose screws and misaligned mounts on top of the cant problem, you’ll be lucky to even get the gun to stay on paper more than three out of five times.

But if you focus on stability, alignment and proper torque during installation, the rifle has a chance to shine. Get them wrong, and you’re troubleshooting phantom problems every time you shoot. I’ve often wondered how many rifles have been sold cheaply because “This thing just won’t shoot,” when it was actually just a scope mounting problem.

Just Do It — Or Not

There’s no way around it: to properly mount a scope, you need equipment. One option is to pay a competent gunsmith to do it — money well spent if the gunsmith does it properly — or you can invest $400-700 in proper tools and own them for life. Even if you only mount a couple of scopes a year, it pencils out over time.

The level of care you put into mounting a scope should match the level of accuracy you expect from the rifle. A 100-yard deer rifle deserves good attention, while a high-precision long-range rifle wearing a high-end optic demands discipline, proper tools and patience. Sloppy mounting introduces doubt, and doubt is corrosive to both accuracy and confidence because you end up wondering why the rifle won’t find or hold acceptable accuracy. To unlock a rifle’s true potential, the scope simply must be mounted properly.

The Process

The process starts with slowing down. Looking back over the years, every time I got in a hurry to mount a scope, I eventually ended up taking it off the gun and going through the process again.

Now, I consider mounting a scope much like performing surgery — you need to prepare the “operating room,” lay out your tools, and then take a moment to consider what you’re doing. After taking a deep breath, I shut off my phone, and then once I’m sure all is ready, I will proceed.

First, you need a gun vise or some method of locking the rifle in place to keep it level throughout the mounting process. If you’re ever-so-careful and don’t bump the gun, you might get away with some kind of homemade jig or even a padded stack of books, but the first piece of equipment you should acquire is an honest-to-goodness gun vise. There are some good ones that don’t cost an arm and a leg, plus they come in handy anytime you clean or work on a gun. Every serious shooter needs a gun vise to practice their gun vice!

You need to verify the horizontal and vertical alignment of all these pieces, so a reference method is necessary. This is why serious practitioners will have several types of spirit levels on their bench, ranging from a carpenter “torpedo” level to small magnetic versions that easily cling to receivers and barrels. A smartphone app can work in a pinch, and I sometimes use it simply to triple-verify everything, but you simply cannot proceed in the process without knowing the bore gun is properly aligned in three dimensions. Anything less, even a degree or two, introduces error. And, as shooters, we know that errors are the anathema of accuracy.

Square and True

Ideally, the receiver or barrel has a flat surface someplace known to be square to the bore — use it, but verify by whatever means necessary. I’ve learned to check this every way possible and not assume anything. Whenever I’m mounting a scope, I’ll bet the neighborhood cabinet maker is thinking, “OK, enough with the levels already!” because I am never satisfied I’ve achieved perfection in alignment. At every step in the process, and often in the middle, I re-check the levels just to make sure the rifle or scope didn’t shift as a result of an accidental bump, jolt or slip.

One of those “bass boomers” goes by with his lowered Honda Civic rattling your dishes by pumping out gangster rap at 140 dB? If I’m mounting a scope, I’m going to check the level after he drives by just to be sure.

If I’m not otherwise mounting a scope, I’m tempted to try one of my rifles out on a moving target …

Be sure to dry-fit everything first and check eye relief before the rifle goes into the vise. If you forget, you’ll end up pulling the rifle off the stand after 10 minutes of leveling and then starting over, probably minus a few hairs you plucked out in frustration.

It should go without saying that you should use proper gunsmith screwdrivers so you don’t booger up the screws in the process. Rest assured, if you do mar the screws, you’ll see the nick every time you look down at your rifle for the rest of your days.

One other important note: a torque wrench isn’t optional when mounting a scope, as over-tightening can damage or strip mounts and quietly crush scope tubes without warning.

Down to Business

Once the scope rings are mounted, verify they are aligned using alignment bars — the pencil-shaped rods with pointed ends. The rods are slipped into the rings so you can see how close the points meet together in the center. You’ll often be surprised by how out of alignment the set is, and you’ll need to make adjustments.

By the way, don’t use the scope itself as a wrench when installing twist-lock bases. I shouldn’t have to say this, but scope manufacturers tell me this misuse leads to one of the more common warranty claims. And “Gee, I didn’t know” usually is not enough for a free scope replacement!

Now that the front and rear mounts appear to line up nicely, you will lap the rings lightly with a lapping bar and compound to smooth out the final lumps, bumps and minor misalignments. If you’ve never done it, lapping involves running a perfectly-sized steel bar lightly covered in abrasive paste back-and-forth through the rings.

Here, your goal isn’t to remove material so much as it is to “reveal the truth.” After a few passes of the lapping bar, the shiny spots will tell you everything you need to know about the machining tolerances of rings. If the rings look wildly out of line with regard to where material is being removed, or a considerable amount of material is being removed from one location, immediately stop, back up and check the whole setup for alignment. That, or you’ve got a lousy set of rings — and it does happen!

By the way, if you’re OCD and spend an hour lapping the rings to a nice, smooth, glass-like finish, you’re actually reducing the gripping force to resist recoil. You want everything to play nicely together, but the rings don’t need to be polished like a hydraulic piston shaft.

Once you’ve finished lapping, clean everything up. I always wear nitrile gloves and dedicate an entire roll of paper towel to this task because lapping compound seems to be even messier than a room full of 4-year-olds after they’ve gorged on chocolate birthday cake.

After things are spotlessly clean, it’s time to mount the scope loosely in the rings. Tighten the screws only enough to engage the rings, but with virtually no torque. You will then level the reticle in the horizontal and vertical planes. The scope should be loose enough you can carefully turn it to line up with your reference marks, but without disturbing the rifle. Tread lightly here and make small adjustments rather than grabbing the scope and giving it a good twist.

Light it Up

One method for obtaining alignment is to shine a light backward through the scope onto a wall, then use a plumb bob to verify the true vertical of the resulting reticle shadow. There are also professional tools and kits that use the same principle much more accurately. If you don’t have tools or you’re trying to fix a sudden problem at elk camp, looking at a makeshift plumb bob downrange can come close, provided you know the rifle is held truly vertical.

When you are satisfied everything is well and truly “right,” tighten the ring screws to torque using a torque wrench and sparingly apply a tiny drop of blue threadlocker (the removable kind) onto the screws to keep them in place. Ring screws typically require 15-25 inch-pounds of torque, which is barely snug by hand, but always refer to the specs that came in the package with the rings. When you start snugging things down for good, guessing becomes the moment where mistakes become permanent, non-recoverable damage.

If you took your time, used the right tools, and made sure everything was done properly, you can sit back and let out a long-held breath — your scope should be secure, leveled and ready to go.

Doing It Right

Why all this matters becomes obvious later, typically much later. A mysterious shifting point of impact over time can often be traced to either a slight change in ring/mount torque or a scope tube damaged during mounting. Even more insidious is when the scope isn’t mounted perfectly square and true to the bore. When this happens, you find every click of windage or elevation is a bit different through the range of adjustment. A ¼-MOA click might become 0.1 at the center but maybe 0.5 at the extreme end of the scope adjustment. Imagine chasing this problem as you try to figure out why the gun is on paper at 100 yards but misses by a country mile at 500.

This is how shooters lose confidence in equipment that never really got a fair chance.

So, herein endeth the sermon. Go slow, spend the money and give the mounting process the attention it truly deserves in order to make sure your expensive scope doesn’t end up as the problem instead of “the” solution.

Mounted correctly, the scope will faithfully do its job without fanfare and help keep you a little more sane. Done wrong, it can haunt every shot. The difference isn’t magic — it’s patience, proper equipment and refusing to accept “good ’nuff” in an endeavor where precision is the literal point.

Want more online exclusives from GUNS delivered straight to your inbox? Sign up for our FREE weekly email newsletters.