How to Mount Shotgun Optics

There are a few ways to get red dots, reflex sights, and scopes on a shotgun. Here’s how to choose based on application.

You don’t often find optics on shotguns. Because they fire multiple projectiles at once, pinpoint accuracy isn’t usually required. If you’re doing any sort of wing shooting or busting clays, they probably would do more harm than good, forcing you to aim when you should be concentrating on following through. But when the target is relatively stationary, an optic of some sort can really be a benefit.

The magnification a scope provides is welcome in the deer woods, especially on a slug gun, helping you make distant shots with greater ease. Turkey hunters employ ultra-tight chokes that keep patterns narrow out to 40 yards and beyond, so knowing your exact point of aim is essential for them. And with the growth in 3-gun contests, more and more competitors are looking to reflex sights to help them get on target faster in competitions where seconds count.

Types of Shotgun Optics

There are a few different types of optics that can be used on shotguns. Each has their strengths and weaknesses, so I’ll go over each and you can decide which best suits your usage. Like most types of equipment, there isn’t one that will be ideal in every situation. You’ll need to decide what the shotgun will be used for most of the time and make your choice based on that.

Scopes

nikon slug hunter 3 cantilever mount
This is the Nikon Slug Hunter 3-9x40 BDC200 on a cantilever mount.Nikon

Traditional scopes have their place on shotguns, especially if they are used to shoot slugs. Just as with a rifle, the magnification they provide is beyond useful when dealing with distant targets, and can help you notice impediments to your projectile's flight path, such as small branches or other brush, that you might miss with your naked eye.

While slugs typically fly further than shot will, the effects of gravity on the heavy projectiles keeps their effective range well below that of a centerfire rifle. Turkey hunters can also benefit from a scope, as the narrow spread of pellets can make missing easy, even at close range.

When choosing a scope for deer or turkey gun duty, the model with the most magnification probably isn’t the best choice. A quick online search will show you that most scopes designed for scattergun use are somewhere in the neighborhood of 1.5x to 7x magnification, which is more than enough for deer-sized game out to 100 yards.

Because of the lower magnification range, the objective lens doesn’t need to be large to gather enough light to be effective in the low-light periods when animals end to be most active. Most are in the 20 to 33mm sizes, which keeps the scope low profile: a plus when traversing brushy countryside.

nikon pro staff bdc reticle
The Nikon Pro Staff 27x32 BDC ReticleNikon

When it comes to reticles, the sky is the limit, with manufacturers churning out myriad designs for nearly any imaginable scenario. But with shot distances being rather close, there’s no need for elaborate designs that provide enough holdover to hit a man-sized target some 2,000 yards.

If you plan on using the shotgun for slugs, a simple duplex reticle is more than sufficient, though there a few excellent models on the market with bullet drop reticles specifically designed for the weighty projectiles. If you routinely take longer shots with your shotgun, these are a solid choice.

Turkey hunters have quite a few choices in designs, ranging from simple dots to diamond-shaped reticles that you place right over the bird’s head.

Prism Sights

The Burris AR-332 3x32 Prism Sight
The Burris AR-332 3x32 Prism SightBurris

Prism sights, commonly referred to as red dots, are similar to scopes in appearance but use a prism instead of a series of lenses to form the image you see in the eyepiece. Because of this, prism sights are more compact and typically feature somewhat greater eye relief than traditional scopes. These optics feature little or no magnification, with anywhere from 1x to 3x being common. There is a great variation in reticle design, either etched or illuminated. Most hunters prefer an etched design that doesn't completely rely on batteries.

The prism sights intended for close-quarter use on AR-platform rifles are actually pretty well suited to shotgun use. For slug hunters in brushy country where shot opportunities seemingly crop up out of nowhere, the rapid target acquisition and slight magnification can greatly aid in getting on targets in the 50-yard range quickly. For close range or fast moving targets, such as running coyotes, go with a model with no magnification. The same goes for 3-Gun.

Reflex

The Nikon P Spur Tactical
The Nikon P Spur Tactical Nikon

Reflex sights are seemingly standard equipment on the pistols used in 3-Gun and other shooting competitions, and have made their way over to the some concealed carry holsters. Because you don’t need to align your eye along the sight axis like would with iron sights, you can keep both of your eyes open, which gives you more situational awareness and greater depth of field.

In addition, there are no eye relief requirements on a reflex sight; they can be as close or as far away from your eye as mounting options will allow. The downside is that reflex sights offer no magnification, so they are only suited to close distances.

Crimson Trace CTS 1100 sight
The new Crimson Trace CTS 1100 sight.Crimson Trace

In a reflex sight the aiming point projected forward onto a lens, which reflects it back toward the shooter, allowing them to take aim. There are two main types, exposed and tube-style reflex sights. The most common is the open variety, which is easily identified by the small, open window that the aiming point is projected on. These are among the smallest form factors, and for this reason it’s what you’ll find on pistols most often.

Though larger, the tube style has an advantage over the open models. There are two lenses in the tube configuration, which contains the beam of light used to project the aiming point. Because it’s in a contained environment, tritium, the glow-in-the-dark compound used for everything from illuminating watches to accelerating nuclear reactions, can be used in lieu of a battery-operated light source.

Holographic Sights

EOTech XPS2 Sage Holographic sight
The EOTech XPS2 Sage Holographic sight.EOTech

Though not as common as reflex or prism sights on hunting guns, holographic sights have a devout following, probably thanks to their use by the military. Though similar in appearance to a reflex model, this type of sight provides an aiming point by using a laser to illuminate a holographic film suspended between plates of glass. This makes these sights very precise, but still allows the shooter to keep both eyes open.

One issue with holographic sights is battery life. Lasers require much more power to run than light emitting diodes (LED), which is what the other sights employ. As such, run times are significantly less. Price is another concern; with holographic models costing orders of magnitude more than exposed reflex makes.

eotech mounted on shotgun
The EOTech mounted on a shotgun.EOTech

Mounting

There’s more a few ways to outfit your scattergun with a scope or other optic. What method you choose is driven mostly by the gun’s intended use, and choice of optic. Once again, you’ll need to be honest with yourself about what you will be doing with the gun the majority of the time.

Tapped Receiver

Many shotguns, especially turkey or deer specific models, now come with receivers that have already been drilled and tapped to for a rail of some sort. This makes mounting an optic easy; simply select the correct rail for your shotgun and install it by tightening a few screws. Some tactical models ship with the rail already installed, so all you need to do is attach your optic and hit the range.

benelli m4 tapped receiver
This Benelli M4 has a tapped receiver, allowing a rail to be screwed right on.Benelli

If yours isn’t so equipped, you may be able to have the receiver drilled and tapped by a gunsmith. The material that comprises the receiver is the biggest factor in whether this can be done. If the receiver is steel, you’re probably good to go. It’s possible to tap aluminum, but it must be somewhat thick to stand up to the torque exerted by the screws. If you have an ultra light gun, this probably won’t work for you.

The process isn’t terribly difficult, and can even be accomplished in a home shop if you have decent drill press outfitted with a vise sturdy enough to keep the receiver steady. Select a rail that matches the gun’s contours and fits lengthwise, and center on the receiver. Mark the location of the holes and prepare to pass the point of no return.

Drill and tap holes for 8-40 screws, which are among the larger sizes commonly use to mount rails. These will hold better in aluminum than thinner ones. After the screws are in place, you’ll probably need to sand them level with the inside of the receiver so they don’t interfere with the operation of the bolt. If any of this sounds intimidating, take it to a competent gunsmith or select one of the methods listed below.

Cantilever Mount

cantilever barrel rail
A shotgun barrel with a cantilever rail mount attached.huntfishcampsupply.com

The traditional solution to mounting a scope on a shotgun is a cantilever barrel. Instead of being attached to the receiver, the optic rides a rail that is welded to the barrel itself. This allows you to swap barrels based on the shotgun’s intended use at any given time, choosing a rifled barrel for slugs and a smoothbore for ducks and doves. Because the optic stays with the barrel, there’s no need to re-zero it every time you switch back and forth, like you would need to if you removed it from the receiver.

Many shotguns come in combo form, shipping with a 26 or 28 inch barrel for wing shooting and a shorter, rifled cantilever barrel. Some feature a short smoothbore barrel for turkey hunting, though this also makes for a good home defense set up. For a budding outdoorsman, these represent a great value, allowing you to use the same gun year round. The Remington 870 and Mossberg 500 combos are excellent examples of this, and have provided countless sportsmen and women with their first shotgun.

Saddle Mounts

saddle optics remington 1100
This is a saddle optics mount for a Remington 1100 from Safariland.Safariland

As the name implies, a saddle mount straddles the receiver and provides a solid platform to mount an optic. These use existing holes to attach to the receiver, making them a great choice for the do-it-yourselfer. While slightly more involved than removing a cantilever barrel, you can take the optic off if you decide you don’t need it, though unlike a cantilever setup, you should make certain to re-zero the optic wen you re-mount it. And because you don’t permanently modify the gun in any way they don’t affect resale value, if that’s a concern of yours.

Rib Mounts

aimpoint rib mount
This Aimpoint sight can be mounted directly to the rib of a shotgun.Aimpoint

A recent introduction to the shotgun optics world is the rib mount. As the name implies, these devices pinch the shotgun’s rib and provide a Picatinny or Weaver-style rail to install an opti, or the mount allows the optic itself to me clamped right to the rib.

Because the metal they attach to is relatively thin, they must be used in conjunction with a lightweight optic. Eye relief is also concern, as the optic is positioned far forward, in what Col. Jeff Cooper would describe as the Scout position. But if you want to add an exposed reflex sight to your shotgun with a minimum of fuss, these are a great option.

My Build

benelli mount with nikon
The author upgraded his go-to turkey gun with an optic, Nikon’s P Spur Tactical open reflex sight.Joseph Albanese

After a decade, I decided it was time to give my turkey gun an upgrade. The Benelli Nova has bested its share of Toms in stock trim, but I decided to breathe new life into the pump. When turkey hunting, you often find yourself contorting into some unusual positions to get a good shot, so an optic with the ability to position my head nearly anywhere and still put my shot where I wanted it seems like a great idea.

The short barrel also makes it a good choice for home defense, so I wanted an optic that would perform well if something ever went bump in the night.

Reflex sights are an excellent choice on shotguns used for anything from home defense to hunting. More than a few 3-gun scatterguns are so equipped because they allow the competitor to cycle through targets so quickly. While I only plan on taking one turkey at a time, I went with Nikon’s P Spur Tactical open reflex sight for my gobbler gun upgrade. The Spur features a fully multicoated lens that eliminates that blue tint found on many reflex sights, and has a wide field of view. The aiming point is a fully adjustable 3 MOA red dot with 10 brightness settings, and the battery will last for over 15,000 hours of continuous use.

For a mount, I went with one of Aimtech’s saddles. The metal on the Nova’s receiver is thick enough to be tapped, but I went for the ease of installation the saddle provides. Attaching the mount took less time than it would to disassemble the gun, and was considerably easier.

The two half pins used on the front of the saddle mean you can’t accidentally over tighten the mount and cause the action to bind. And the entire assembly is easy to remove if I ever decide I want to ditch the optic for whatever reason. I could also pull the whole package off if I ever decide to sell the gun, but I doubt that will ever happen. I believe the correct number of guns one should own is calculated using this simple formula: n + 1, where n = the number of guns you currently own.