There’s More to Them Than Meets the Eye

An optical collimator comes in very handy when mounting scopes at a typical garage workbench lacking sufficient room for a laser beam.

Apparently, the mere idea of an optical bore-sighter angers some shooters because they feel they can do the job the old-fashioned way — without the help of any contraption.

It’s all so simple: Just remove the bolt, set the rifle on a rest, look through the bore at a bullseye (or even the peak of your neighbor’s roof), then adjust the scope until the reticle points there too. Done!

Well, yeah — if you have a bolt-action or falling-block rifle, where you can look through the rear of the bore. But with a lever-action, pump or semi-auto, “looking” through the bore requires a tiny mirror, and believe me, the process is a pain in the butt.

Plus, the highest and best use of a “bore-sighter” isn’t preliminary scope adjustment. Instead, they help most during scope mounting, by aligning the centered reticle with the bore. This ensures plenty of adjustment when actually sighting-in (no “running out of clicks” when zeroing).

Average deer hunters usually blame the scope or the “crooked” mount-screw holes on the rifle, but the real problem is usually not mounting the scope properly. Plus, scope adjustments work most accurately and consistently when the erector tube (the part pushed around by the adjustment turrets) is centered inside the scope, not way off to the side.

While correct mounting can be accomplished without an optical bore-sighter, the process requires far more aiming room than most of us have around our workbench. In my early 20s I lived in a house where my bench vise allowed a window-view of the apex of my neighbor’s roof, a handy “target” for bore-sighting, but I haven’t been as lucky since.

A collimator really helps when mounting a scope with Burris Signature ring-inserts, by determining
which inserts line up the scope most precisely.

What’s In A Name?

Before going further, the term “bore-sighter” isn’t very accurate, since contrary to what some shooters believe, the gadget does not sight-in our rifle except by pure chance. This can be easily demonstrated by attaching a collimator to several range-sighted rifles: The collimator will point in a slightly different direction on each rifle, because during firing rifles recoil and barrels flex.

However, we can derive an average “point of impact” with a given bore-sighter when making the same test. This is exactly why some people (including me) call bore-sighters collimators. “Collimate” means aligning two lines.

Back when I acquired my first collimator, they all consisted of a rod inserted into the rifle’s muzzle, with the rod connected to an optical screen containing a grid-reticle. I still have that first Bushnell collimator, and use it more than my others, partly because it works, but also because I sighted it in long ago. With my old Bushnell (and its present version) the screen’s grid can be screw-adjusted to the average point-of-impact of several rifles.

Today we can buy several other types of collimators, partly because some shooters object to inserting a steel rod into their rifle barrels, possibly damaging the bore. I haven’t found any evidence of this yet, either in my Hawkeye bore-scope or the way my rifles shoot, but there it is.

Consequently, many of today’s collimators attach to the muzzle with a flat magnet, and either use an optical screen or a laser beam. I have collimators of both types, and while magnet models do work, they depend on the squareness of the muzzle to the bore, whether the barrel’s crown, a brake or a suppressor. The latter two, in particular, don’t always line up perfectly with the bore, but magnet collimators come in handy when the rod on my Bushnell can’t reach the bore. I also used magnet collimators on shotgun slug barrels, with bores too large for any collimator rod.

Laser collimators also require some distance in front of the muzzle. Normally this isn’t as far as the neighbor’s house, but a few yards are far longer than the few inches of a screen collimator.

This laser collimator from Wheeler Engineering uses a magnet to the muzzle, but some laser models
fit inside specific rifle chambers, shining the beam through the bore.

John’s been using this Bushnell collimator for many years. Its grid can be “sighted-in” by adjusting some screws.

Mount It Straight

There are two basic methods for centering a scope’s reticle. Either twist the turrets while counting revolutions, or place the front bell against a mirror, then look through the scope. Unless by some chance the reticle’s already centered, you’ll see two of ’em — the reticle inside the scope, plus its reflection in the mirror. Turn the turrets until the pair of reticles line up and the adjustments should be centered — though not always, due to imperfections in the scope’s construction.

With the adjustments centered, you can find out if the scope’s mounts result in the reticle being reasonably centered in the collimator. If not, various methods can be used to realign the scope, from old-fashioned shims to Burris’s nifty Signature ring-inserts (they’re made of polymer so they won’t scratch your precious scope).

Using a collimator while mounting scopes not only bypasses the possibility of running out of clicks on sight-in day, but allows your scope’s clicks to work most consistently, far more important these days than it used to be, with so many shooters cranking their scope’s elevation turret to shoot at longer ranges. Both are preferable to driving all the way to the range and discovering your scope doesn’t work right.

Burris Optics, Ph.: (888) 440-0244

Bushnell, Ph.: (800) 423-3537

Wheeler Engineering, Ph.: (877) 509-9160

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