Crossbow Scopes Explained

Being able to scope your crossbow is what in part makes them such effective one-shot hunting weapons. And the good news is that for anyone even remotely familiar with conventional firearm scopes, using and sighting crossbow scopes is straightforward – although you may need to become a bit more comfortable with range-finding if you are shooting much past 20 yards. Let’s take a closer look at these scopes and how to use them.

Anatomy of a Crossbow Scope

As the beautiful Nikon Bolt BDC60 XR Crossbow Scope above illustrates, there are some key parts of a crossbow scope that you should be aware of:

  • Ocular Bell – this is the eyepiece, which houses the ocular lens that you look through when aiming;
  • Objective Bell – the lens (often with variable magnification) that is furthest away from you when aiming. In general, the larger the objective the more light it can gather;
  • Windage Knob – the adjustment used to vary horizontal shot placement when sighting in the scope;
  • Elevation Knob – the adjustment used to vary vertical shot placement – i.e., this is what bring your shots up or down as necessary to align your target with the reticle.

Crossbow Scope Reticles

A simple but effective mil-dot scope used for the Nikon BDC 60 crossbow scope.

The cross hairs (or dots as they may be) come in a variety of configurations, with some illuminated in a wide range of colors. Whatever type you choose, they should be such that the “hairs” or “dots” are not so large so as to obscure the target, and not so fine or small that they are lost against dark targets/backgrounds. In addition, you generally want a reticle configuration that allows for basic rangefinding. Rangefinding reticles have a series of dots or lower slashes/hairs below the main center hair/dot. More about that below.

Zeroing (sighting-in) Your Scope

A good scope can do wonders to your accuracy, and can provide a big, bright picture of your quarry to lock onto. But you need to first have an idea of the ranges that you’ll likely be taking game at. If you are getting started with crossbows or archery – or simply want to take the conservative route (which we generally recommend) – try and adjust your “zero” or hunting “sweet spot” to 20 yards. This is the distance at which we want to nail the bullseye when the scope crosshairs (or uppermost red dot) is fixed on the target.
Why is this important? It’s because, depending on your setup and arrow configuration, your arrow may need to fly above the target and then drop to the bullseye – something that becomes more obvious if aiming at more distant objects

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But let’s not get too far ahead of ourselves. The first task is to see if our scope (out of the box) is in the right ballpark.

Step 1 – Course Adjustment

Once you’ve installed it, place a target at close range, no more than 10 yards away. Now we want to shoot some “groups.” Grouping shots is the traditional way of determining how a weapon (including a firearm) is shooting. It usually involves taking 3-5 shots in a sequence from the same spot and with no changes to the rig or arrows. This does two things, it helps minimize random twitches and other issues with the user, and establishes how consistent your rig is overall. As you might guess, the tighter the groups you shoot the better – and you should measure them by placing a ruler between the outermost shots to properly determine the “spread.” If you can group your shots with spreads of 4 inches or less, you are doing a good job!

If, upon shooting your first groups, you notice that you are not coming anywhere close to the bullseye, this could indicate that scope is not mounted properly. Go back and check that everything is where it’s supposed to be, and tightened down correctly (use a thread locker if necessary). If the scope is mounted right, then you may need to make some course adjustments to the elevation (vertical adjustment) or windage (horizontal adjustment) knobs to get things back to reality. Ordinarily you will want to turn these gradually, but in the case of missing badly, you can turn them one or more full revolutions until necessary, then turn a handful of “clicks” or less to get you right on target. Some like to calculate how many clicks are need to find the bullseye, but I find its better to simply adjust and test – and repeat as needed!

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Step 2 – Fine Adjustment & Zeroing

Now that you’ve reached the point where you are grouping 3 or more shots well around the bullseye, it’s time to zero the scope in for more practical shooting. Since we are assuming here that most of our shooting will occur within 20 yards, that will be our zero in this example (20 yards is ideal for most shooters). So now we need to bring the target out to 20 yards and keep shooting groups  – and using finer adjustments to the windage/elevation as needed – to get us hitting the bullseye reliably. Remember, if you are using a reticle with multiple dots or crosshair “pins,” you want to set things up so you are on the uppermost dot/pin at this point.

Using the Reticle for Rangefinding

A typical rangfinder reticle configuration: notice the slashes below the crosshairs signifiying addtional 10-yard increments from "zero."

Now just because you are setting your scope for “zero” at 20 yards doesn’t mean that a fat buck that presents itself broadside at 30 is something you should necessarily pass on. In such case, if you’ve got a suitable reticle with additional pins/hairs/dots, it’s usually just a matter of raising your rig so the target is now lined up with the next lower mark. And if you need (and are comfortable with) taking a 40 yard shot, you would raise the scope some more so the sights fix over the next lower pin, and so forth.

As you can see, for most reticles, each dot or additional pin roughly approximates additional 10-yards of distance. This does take a bit of practice, but can be very effective to take advantage of longer-range opportunities when they arise without having to reset the scope ahead of time.

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A Scope Does Not Make Your Crossbow a Rifle!

Just a friendly reminder for those starting out – a scope still doesn’t change the fact that crossbows are short-range weapons! Indeed, even the most innocuous conventional firearm, let’s say a .22 rimfire, can reach velocities exceeding 1000 fps, which is roughly three times faster than that of the most powerful crossbows (especially if shooting properly-weighted arrows that can kill game).

As such, the comparatively sluggish travel of crossbow bolts, by definition, makes them accurate enough for shooting up to a maximum of 40 yards or so – and this is only with considerable practice range-finding to boot! Yes, kills at 50 and 60 yards are possible for skilled shooters and high-powered rigs, but for most people, this is a reckless exercise that, at best, amounts to a lucky shot and, at worst, is likely to simply wound a game animal and cause needless suffering. Do yourself a favor and, scope or no scope; use your crossbow at close ranges where it’s most effective!