Glocks rule the roost of the aftermarket world, enough so that other guns use their parts and magazines due to the commonality. Typically, that’s handguns, but with the Defender Tactical CoSight, you can add Glock sights to your Mossberg shotgun. Glock sights offer you all sorts of options, including night sights, suppressor-height sights, blacked-out sights, and so many more. Heck, Glock even has ghost ring sights. Beyond Glock sights, it also acts as a red dot mount for optics with the Trijicon RMR footprint.
Bias is a real thing that we all have. I love CZ’s weapons and tend to be biased toward their guns. That’s usually fine, but you should be aware of bias. Today’s bias is a little more personal. I teamed up with Defender Tactical to design something called the CoSight. To be fair, they did most of the work, and I simply contributed where I could. With that said, I make no money on the sales of the CoSight, but I do get free CoSights for my shotguns.
Since I’m tied to this, you may choose not to believe my review, but to be honest, if it didn’t work well, I wouldn’t mention it out of embarrassment. Also, the folks at Defender Tactical are serious about their quality control, and they would have given me the bad news during the prototyping stage. With that said, let’s add Glock sights to a shotgun.
The Defender Tactical CoSight: The Problems It Solves
I actually mounted this sight to a Shockwave, which isn’t technically a shotgun, but it’s still in the Mossberg 500 family. The CoSight does a few things beneficial to Mossberg shotgun owners. First, it allows you to mount a red dot, specifically an RMR pattern red dot. It allows for the use of Glock sights to Cowitness with your red dot. Red dots rule, but having a backup sight option is always handy.
In using Glock sights, we have a myriad of options—night sights, big dot sights, ghost rings, etc. Standard height sights will Cowtiness through most open emitter Trijicon RMR footprinted optics, including the Holosun 507C.
These sights also sit higher than a typical Mossberg bead sight, which fixes the issue Mossberg has with slugs and modern loads like Flitecontrol seemingly hitting high on target. Open sights are also quite fast, and pistol sights work well on shotguns at shotgun ranges. The presence of a rear sight also helps ensure precision with modern loads and slugs. It’s not as precise as a ghost ring, but it tends to be faster.
Mounting Up
The CoSight comes with or without sights. You can order with the sights preinstalled or order just the CoSight and pick and choose your own Glock sights to fit. If you have something like a 590 with ghost ring sights, you can continue to use your front sight and replace the rear ghost ring with the CoSight, and a suppressor height Glock sight will work with your front sight.
The CoSight attaches to your Mossberg receiver the same way an optic’s rail would. It’s easy to attach and takes all of five seconds to do. You have to add your Glock sights first, and then you can install it to the gun. Once mounted, you can then add your red dot. As you can see, I didn’t use a red dot for my testing.
The reason why is simple. We all know red dots work, and they work well on shotguns. I wanted to know if the CoSight was going to work, and if it did work, how well it would work with just Glock sights. I figured the position on a Shockwave would make it even more interesting and challenging.
At the Range With the CoSight
To start, I did some basic accuracy testing with buckshot. How do the point of aim and point of impact work with various loads? I started with a bare-bones Federal buckshot. It’s a nine-pellet, full-powered load without any fancy wads or shot cups. Using the Glock sights and a torso target, I got near-perfect point of aim to point of impact. Two rounds patterned slightly to the left.
I then tossed in my favorite load, Federal Flitecontrol, and tested it once more. With the Shockwave, the typical problem was the load appearing to hit way over where I was aiming while using the standard sight. With short barrels, the issue gets worse. With the CoSight, there was no issue. It landed right where the front sight was aiming. It was dead on.
If You’re Not First, You’re Last
So, it works for accuracy, but what about speed? The idea behind using open pistol sights is that they tend to be quite fast on target. It takes a little less time than a peep sight, especially on a stockless shotgun where you don’t get the comfort of a cheek rest. At 10 yards, I used an IPSC target and some bare-bones buckshot starting in the low ready.
I used a shot timer, and my accuracy standard was to put most of the shot in the A-zone of the target. At first, I was so used to using the bead at the end of the barrel that I was focusing past my sights. It took a few reps to get used to the front sight being much closer to my face.
Once I figured it out, I was able to get a dose of buckshot on target in about 1.2 seconds. With a stock or more practice, it would easily be less than a second. The short sight radius makes it quick to line up, and at what’s basically handgun range, it’s more than precise enough to put lead into the center of a target.
What if we go back a little further and fire slugs from 25 yards? Reduced recoil slugs, because I’m not a masochist. Again, low ready with accuracy standards saying hit them in the chest. With all that practice I got with buckshot, I was able to be surprisingly fast with slugs. I even landed one shot in 1.58 seconds directly to the chest, although most hovered closer to the 1.7-second mark.
Blasting Away
The CoSight is what I’ve always wanted from shotgun sights. It’s rugged, reliable, and accepts common and affordable sight options. It makes mounting an optic easy and allows you to keep a usable set of sights on your gun. I might be biased, but if you tend to like shotguns and want a better sighting option than just a bead or want an easy optic mount, then this may just be the accessory for you!
