Open vs Enclosed Emitter Red Dot Sights

If you’ve ever wondered whether you need an enclosed or open emitter red dot optic for your pistol or an offset mount on your AR-15, hopefully, this article can help make your decision a little easier. My advice is based on my personal experience. Still, I try to get out and shoot in snow, rain, and different conditions to develop stronger, more informed opinions about these optic setups.

There are many different options on the market these days, and enclosed emitter optics are very beneficial because they protect the red dot emitter, which is what projects the red dot onto the pane of glass that your eye sees. Open emitter optics have been around for a very long time, have proven themselves in many austere environments, and work quite well. They’re also usually more affordable than enclosed emitter optics.

As an example of an open emitter red dot optic, check out the Trijicon RMR HRS. It has one pane of glass in the front, and there is nothing in the back protecting the red dot emitter, which is the LED module that projects the red dot onto the glass. Rain, snow, debris, dust, or similar substances can get into the optic between the emitter and the glass and occlude the red dot. An enclosed emitter, such as the Meprolight MPO PRO-F, has a pane of glass on both the front and back ends, and the optic housing covers the rest. The red dot emitter is inside and cannot be occluded by rain, dirt, snow, dust, or any other such substance.

Most of these types of optics, enclosed or open, are being used on pistols because that's what they were originally developed for. To me, the emitter design doesn’t matter as much on a pistol as it might on rifles. On my Beretta M9A4, I have an open emitter optic. I currently have it holstered in a T-Rex Arms Ragnarok holster, which does not protect the red dot optic. The optic is exposed to the elements when I carry the gun this way. If it’s snowing or raining, there’s a good chance the red dot emitter will become occluded. If I decided to wear this as my duty pistol on an outside-the-waistband holster, knowing I may encounter harsh weather or extreme environments, this may not be my best option. Now, that may sound like an argument for emitter design mattering MORE on pistols, but an enclosed emitter isn’t necessarily my only other option. For pistols, there are holsters out there that can help protect the optic. For example, I have a Safariland SafariVault holster I use with my Glock 45 that has a flip-up cover attached that can close over the optic and help protect it. It does not fully protect it, but it can significantly reduce the amount of rain, snow, or other debris that can fall directly into the optic housing. This is a good option if you run an open-emitter optic in a duty-style holster outside the waistband.

Also, most civilians who carry, do so concealed, which is an important consideration in the discussion of whether an enclosed optic is necessary. I generally carry my Glock 45 with a Vortex Defender-XL optic in a concealed carry IWB (inside the waistband) holster. In this configuration, it doesn't matter if the emitter is open: it’s covered by garments – at least by a shirt. In most common situations, there is little chance of the red dot sight becoming exposed to excessive water, dirt, mud, dust, or other elements. I haven't noticed a difference between using an open and an enclosed emitter for concealed carry. To verify, I took this gun in this exact setup out on a day when it was raining and snowing simultaneously and did some shooting drills. I did a lot of drawing from the holster, shooting strings of five shots, re-holstering, doing additional draws, etc. While going through two full magazines, I only got a little moisture in the optic window, but not enough to occlude the red dot sight. An open emitter optic is perfectly suitable for concealed carry and can save you quite a bit of money. Most of the enclosed optic designs from higher-end manufacturers tend to cost more. I don't have to spend the extra money to get something like an Aimpoint ACRO P-2 on this pistol if it’s in that concealed carry role.

On the other hand, there are use cases where an enclosed pistol optic matters more. I have a Smith and Wesson M&P Performance Center 10mm with a Holosun SCS-320 optic, which is an enclosed optic. It’s meant to be like a woods gun, something you take with you out in the backcountry and wear outside the waistband, so enclosing the emitter is my preference and recommendation for that use. Also, if you can and want to go the extra mile, it won’t hurt you to have an enclosed optic. Aside from cost, it will always be a benefit to some degree. It carries a different risk, though; if it ever loses its seal or leaks and the nitrogen somehow comes out, and moisture gets in there, you're out of luck, and you have to send it back to the manufacturer because there's no other way to fix that. I haven’t had that happen yet, but I shoot a lot of enclosed optics, so I’m kind of waiting for that day. I have a feeling it will come eventually—especially since this is a niche pistol and not one I can easily find holsters for, let alone a holster with a protective shroud for the red dot sight.

Enclosed optics have benefits, but I would say you can get away with an open emitter on handguns for most applications. Regarding rifles, I have not found that to be the case. I have a BCM RECCE-16 with a fully enclosed emitter Meprolight MPO PRO-F red dot optic piggyback mounted on top of an LPVO. It's a relatively new closed-emitter red dot optic. Before I had this particular optic mounted, I had the Trijicon RMR piggyback mounted instead. It’s an excellent optic (the Trijicon RMR is legendary), but when you carry a rifle, especially out in harsh conditions, you usually have it slung so the rifle's pointed downward. An open emitter optic is wide open, and whatever drops out of the sky can fall right into the housing. I've been out in the snow and the rain and other conditions where that exact thing has happened. Then you pick up your rifle, and your optic is full of snow or water, so you either don’t have a sight picture at all, or water droplets disperse the red dot. Because of that, I switched from an open emitter to an enclosed emitter optic on my rifle in the offset position. Having red dot optics that are generally designed for pistols on a rifle can help with close combat scenarios, as well as passive use with night optics, where you would otherwise only have a magnified scope, so it’s definitely a good thing—but only if it works. If you're going to put a pistol red dot on a rifle, I highly recommend you get an enclosed emitter if possible.

--Magic Prepper