Exploring the Differences Between Enclosed and Open Emitter Sights

Exploring the Differences Between Enclosed and Open Emitter Sights

Hey all, we here at True Shot Academy are going to talk about pistol-mounted red dot sights today. The market for micro red dots has expanded dramatically in recent years, with manufacturers offering two distinct design approaches: enclosed emitter and open emitter systems. Today we will explore the differences between these designs, examine their advantages and limitations, and highlight popular models, and more. Without further ado, let's dive into the world of handgun red dot sights.

Understanding Emitter Systems in Red Dot Sights

Before comparing specific models, it's important to understand how red dot sights actually work. These optics utilize an LED emitter that projects a red (or sometimes green) dot onto a specially coated lens. This creates a parallax-free aiming point that allows for rapid target acquisition with both eyes open. The fundamental difference between enclosed and open emitter designs lies in how this emitter system is housed. Enclosed emitter sights house the LED emitter inside a sealed housing with fully enclosed lens systems, similar to a miniaturized tubular red dot. This design protects the emitter from environmental factors but typically results in a slightly larger and heavier package. Leading examples include the Aimpoint ACRO, Steiner MPS, and Holosun EPS. Open emitter sights feature an LED emitter mounted in an exposed position, typically at the bottom of the sight window, projecting upward onto the lens. This design minimizes size and weight but leaves the emitter exposed to the elements. Popular examples include the Trijicon RMR, Holosun 507C, and Leupold DeltaPoint Pro. Purchase Optics

Enclosed Emitter Red Dot Sights: Advantages and Limitations

Enclosed emitter designs have gained significant traction in recent years, particularly among professional users. These sights offer several compelling advantages: Environmental Protection: The fully sealed housing prevents snow, rain, mud, or debris from affecting the emitter function. This provides peace of mind for duty, defensive, or competition use in adverse conditions. Lens Protection: Both the front and rear lenses gain protection from the housing, reducing the likelihood of damage from impacts or abrasion. Many designs feature protective shrouds extending beyond the lens surfaces. Consistent Performance: The enclosed environment ensures more consistent dot performance across various conditions, including inclement weather, high humidity, or dusty environments. However, enclosed emitter sights come with their own limitations: Size and Weight: Enclosed designs are typically larger and heavier than their open emitter counterparts. The Aimpoint ACRO weighs 1.9 ounces compared to the RMR's 1.2 ounces – a significant difference on a carry pistol. Potential Fogging: In extreme temperature transitions, enclosed optics may experience internal lens fogging until temperatures equilibrate. Quality designs minimize this with nitrogen purging and anti-fog coatings. Higher Average Cost: Enclosed emitter sights generally command premium prices, making them more costly than their open emitter counterparts.

The Aimpoint ACRO

The Aimpoint ACRO (Advanced Compact Reflex Optic) established the enclosed emitter category for pistol-mounted red dots when introduced in 2019. The original P-1 model addressed environmental concerns but suffered from relatively short battery life. The current P-2 version dramatically improved power efficiency while maintaining the same compact form factor. The ACRO features fully enclosed aluminum housing with a 3.5 MOA dot, 10 brightness settings (including 4 night vision compatible), and now delivers an impressive 5-year battery life at setting 6 (of 10). With a high price of entry, the ACRO represents a premium option but delivers Aimpoint's legendary durability and optical clarity. The sight requires its own unique mounting footprint, though adapters for common patterns are widely available. The ACRO's popularity has led several manufacturers to offer direct mounting cuts, though not as universally as the RMR pattern.

The Steiner MPS

The Steiner MPS (Micro Pistol Sight) represents a newer entry in the enclosed emitter category, designed specifically to address user feedback about earlier enclosed designs. The sight features a squared-off housing that reduces perceived bulk, a large viewing window, and a protected but easily accessible side-loading battery compartment. The MPS is a premium optic which offers a 3.3 MOA dot, eight daylight and four night vision settings, and a battery life rating of over 13,000 hours at medium settings. The sight uses the same mounting footprint as the Aimpoint ACRO, allowing for direct compatibility with existing ACRO mounting solutions The MPS has gained traction for its balanced approach to enclosed emitter design, offering environmental protection without excessive bulk. Its squared-off design also prevents snags during holstering and provides a convenient surface for emergency manipulations like one-handed slide racking.

Open Emitter Red Dot Sights: Advantages and Limitations

Open emitter designs dominated the pistol red dot market for years, pioneered by sights like the Trijicon RMR. These sights offer several notable advantages: Weight and Size: Open emitter designs typically present a smaller, lighter footprint due to their minimalist construction. The Trijicon RMR weighs approximately 1.2 ounces, while the Holosun 507C comes in around 1.5 ounces. This reduced weight minimizes impact on pistol balance and makes concealed carry more comfortable. Window Clarity: The open design prevents lens fogging and allows water or debris to clear more easily from the viewing window during active use. Established Footprints: Open emitter sights have established industry-standard mounting patterns like the "RMR footprint," which many handguns now support directly from the factory. However, open emitter designs come with inherent limitations: Environmental Vulnerability: The exposed emitter can be compromised by mud, snow, heavy rain, or debris, potentially rendering the sight inoperable until cleaned. A simple leaf or snowflake landing in precisely the wrong spot can block the emitter. Durability Concerns: While high-quality open emitters like the RMR are extremely tough, the exposed nature of the design creates potential failure points, particularly for duty or defensive use where reliability is paramount. Window Size: Open emitter sights typically feature somewhat smaller viewing windows compared to enclosed designs, potentially limiting field of view and speed of dot acquisition.

The Trijicon RMR

The Trijicon Ruggedized Miniature Reflex (RMR) sight has established itself as the benchmark open emitter design. Originally released in 2009 and updated to the Type 2 in 2017, this sight features a patented housing shape that redirects impact force away from the lens. Available in adjustable LED, dual-illuminated, and type 2 LED variants, the RMR delivers legendary durability in a compact package. With a fluctuating and high price depending on model, the RMR represents a premium option. The sight features multiple brightness settings including automatic adjustment, with dot sizes available in 1.0, 3.25, and 6.5 MOA. Its widespread adoption has made the "RMR footprint" a de facto industry standard, with numerous pistols offering direct mounting capability.

The Holosun HE507C

Holosun's 507C has gained significant popularity by offering advanced features at a more accessible price point. This open emitter sight includes innovations like the Solar Failsafe backup power system, "Shake Awake" technology that conserves battery life, and multiple reticle options including a 32 MOA circle with 2 MOA dot. The 507C utilizes the RMR footprint for broad compatibility while offering features not found on more expensive competitors. Its durable 7075 aluminum housing has proven surprisingly robust in testing, challenging preconceptions about its price-to-performance ratio. The sight's large buttons and side-loading battery tray provide user-friendly operation that many shooters prefer over the RMR's more minimalist interface. Purchase Optics

Practical Applications and Use Case Considerations

Choosing between enclosed and open emitter designs ultimately depends on your specific use case and priorities: Duty/Professional Use: Law enforcement and military users increasingly favor enclosed emitter designs for their all-weather reliability. When a sight must work regardless of conditions, the sealed system provides crucial insurance against environmental interference. Concealed Carry: Open emitter designs still dominate the concealed carry market due to their reduced size and weight. For many CCW users, the smaller footprint outweighs environmental concerns, particularly when the firearm spends most of its time holstered in relatively protected conditions. Competition: Both designs appear in competitive shooting, with open emitters favored for their lighter weight and enclosed emitters valued for reliability across various weather conditions. Outdoor competition shooters often prefer enclosed designs for their all-weather performance. Harsh Environments: Users in extreme environments (maritime, desert, arctic) generally benefit from enclosed emitter designs. The fully sealed systems better resist sand, salt spray, snow, and other environmental challenges that might compromise an open emitter. Training Considerations: Less-experienced red dot users sometimes find the larger windows of enclosed emitters easier for initial dot acquisition. The additional housing can also provide a "framing" effect that helps users consistently present the pistol.

Price and Value Factors

Price considerations span across both categories, with premium and value-oriented options in both designs: Premium Open Emitters: Trijicon RMR, Leupold DeltaPoint Pro Value Open Emitters: Holosun 507C, Olight Osight Premium Enclosed Emitters: Aimpoint ACRO P-2, Steiner MPS Value Enclosed Emitters: Holosun EPS, Shield RMSw While enclosed emitters trend somewhat higher in price, the gap has narrowed as technology advances and more manufacturers enter the market. Consider that some mounts or plates may add $50-100 to any optic's total cost. Of course, milling a slide to allow for optic mounting is also a costly endeavor.

Compatibility and Mounting Options

Mounting systems represent a crucial consideration when selecting a red dot sight. Most modern polymer-framed pistols now offer optional factory optics cuts, with Glock, HK, Smith & Wesson, and Sig Sauer's optics-ready models being among the most common. The Trijicon RMR footprint remains the most widely supported, followed by the Delta Point Pro pattern. Specialized footprints like the ACRO require more specific mounting solutions, though adapter plates are readily available. For non-optics-ready pistols, dovetail mounting systems and gunsmith-installed adapter plates provide viable alternatives. When evaluating compatibility, consider not just the initial mounting but also holster compatibility, co-witnessing with iron sights, and whether your specific pistol model has been tested with your chosen optic.

Conclusion

Both enclosed and open emitter red dot sights offer viable options for modern pistol users, with the choice ultimately depending on specific needs and priorities. Open emitter designs like the Trijicon RMR and Holosun 507C provide compact, lightweight, ruggedized options at the cost of potential environmental vulnerability. Enclosed designs like the Aimpoint ACRO and Steiner MPS deliver superior all-weather reliability in slightly larger packages. For users prioritizing absolute reliability in all conditions, particularly for professional or defensive use, enclosed emitters provide valuable insurance against environmental interference. Those focused on concealed carry comfort or minimizing impact on pistol balance may find open emitter designs more suitable for their needs. All in all, the market now offers excellent options in both categories across various price points. We here at True Shot Ammo carry both enclosed and open emitter red dot sights in addition to our extensive inventory of ammo for sale. Our selection of optics for sale includes offerings from Aimpoint, Steiner, Holosun, EOTech, and more. Additionally, our range of ammunition for sale includes popular calibers and gauges like 9mm, 5.56, 12 gauge, and .22 LR. Whether you want to buy an optic or buy bulk ammo, we have got you covered. As always, happy shooting.