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Guide to Holosun Red Dots with Primary Arms ACSS Vulcan Reticles

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The trend of upgrading firearms with mini reflex sights has gained widespread popularity among enthusiasts. The benefits they provide can take your shooting experience to the next level, enhancing your overall sight picture and making it easier to acquire targets.  

A notable advancement in these sights is the ability to project multiple reticles. For rifle dot style optics, it’s common to see numerous reticle types available, such as the popular circle dot reticle. However, this wasn’t always the case for pistol red dots and mini reflex sights. 

Historically, mini reflex sights lacked diversity, often featuring a simple single-dot reticle with red or green color options. Recent developments, however, have introduced a range of options, including circle-dot reticles and chevron patterns. Despite this diversity, a common challenge persists—the difficulty of locating the dot once it fell out of the field of view. 

Enter the Primary Arms ACSS® Vulcan® reticle. It addresses the issue mentioned above and makes aligning your sight as easy as possible. Below, we’re breaking down the benefits of the ACSS Vulcan Reticle and the Holosun optics that use it.  

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Primary Arms Holosun ACSS 

Collaborating with Holosun, we’ve created top-tier handgun optics featuring our patented ACSS Vulcan reticle. The ACSS Vulcan reticle is the only one available that is designed with a reticle element that sits on the outside of the main field of view. It’s designed this way to help you get on target quicker if your sights aren’t perfectly aligned on target after drawing.  

Given the common occurrence of losing your sight picture with pistol red dots, the ACSS reticle design makes it easier to bring your sight back to the center of the reticle. This way, if you’re off center, you’ll be able to see the curve of the outer circle, making it much easier to track back to the center dot or chevron of the sight.  

What is the ACSS Line of Reticles?  

The Advanced Combined Sighting System (ACSS®) is a high-performance reticle solution to the challenges of modern marksmanship, distilling complex mathematics into intuitive holdovers that enhance your speed and precision. Each ACSS reticle is specially designed to outperform in real-world applications, incorporating a mix of tools to deliver instant firing solutions. These tools may include ballistic drop compensation, auto-ranging stadia, wind holds, moving target leads, or an infinitely precise center chevron. 

Because of the versatility of the ACSS series of reticles, they are used in multiple optic types. Variable power optics, prism scopes, red dots, and mini reflex sights all have options available within the ACSS reticle line.   

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ACSS Vulcan Reticle Overview 

While part of the ACSS line of reticles, the ACSS Vulcan is functionally different from any other in the series. The ACSS Vulcan is purpose-built for mini reflex sights mounted on handguns, as its patented aim-correcting feature is only functional when held at arm’s-length.   

With most pistol optics, if your aim is off target, you likely won’t see your reticle because it’s aiming outside the visible limit of your optic window. This is one of the largest drawbacks to pistol red dots, as it forces the user to break focus on their target, return to iron sights, align their aim, then transition back to the optic. In high-stress, dynamic shooting situations like personal defense, this process is a major point of failure, even among professionals and expert marksmen. 

The ACSS Vulcan solves this problem through its patented outer-circle design. As you can see in the diagram, the ACSS VULCAN appears like a standard chevron or dot reticle when you are aiming properly. However, if your aim drifts off target, such as in a rushed draw or fast movement, you’ll be able to see the edge of the outer circle drift into view. This gives you an immediate reference point for correcting your aim, so you can keep your focus on the target and not have to break away to find your irons.

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Holosun ACSS Optics Overview 

Three of the most popular Holosun optic lines that utilize the ACSS Vulcan reticle are the 507C, 507K and 509. All are great mini reflex/micro reflex sights, but they have their differences that set them apart from each other. Below is the breakdown of each optic:  

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Holosun 507C ACSS Vulcan 

The 507C ACSS Vulcan from Holosun is one of the models available from the incredibly popular 507C line of mini reflex sights. It’s used with full size and compact pistols like the GLOCK 19, SIG Sauer P320, and HKVP9, for example. Though its base plate doesn’t fit every pistol type, there are many adapters and mounting plates that make it compatible with most of the popular 9mm pistols available today.  

The 507C is packed with features. There are 12 brightness settings, including night vision compatible ones, and it has two reticle options, allowing you to disable the outer circle if you’d like. It’s also incredibly lightweight, coming in at only 1.5 ounces. The 507C can have either a red reticle or a green one, depending on the model you choose.  

Regardless of which model you opt for, they each have the same great benefits and would make a great addition to the pistol you add it to.  

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Holosun 507K ACSS Vulcan 

The 507K ACSS Vulcan is very similar in function to the 507C, but there are a few key differences that set them apart—most notably, the size. Holosun’s 507K is a much smaller mini reflex sight (often called a micro reflex). It’s designed to be paired with and mount directly to the slide of most subcompact pistols like the GLOCK 43x/48 MOS, Springfield Hellcat, and SIG Sauer’s P365 series of pistols. Just like the 507C, there is a plethora of different mounting plates and adapters to make the 507K work on most sub-compact pistols.  

Feature-wise, the 507K and 507C are incredibly similar. They both have 12 brightness settings, are compatible with night vision, and have two reticle options. However, they aren’t identical. One of the larger differences, besides the size, is that the 507K doesn’t have any solar failsafe and won’t charge when in direct sunlight. Besides this and the overall size of the optic, there aren’t many other differences. Both use the same battery, but the reticle in the 507K uses a Vulcan Dot instead of the Chevron. Like the 507C, it can be purchased with either a red or green reticle. 

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Holosun 509 ACSS Vulcan 

Another popular option from Holosun is the 509 ACSS Vulcan pistol red dot sight. It shares the same benefits when compared to the 507C, but there are still a few things that set them apart from each other.  

Whereas the 507C and 507K are open mini and micro reflex sights, the 509 series from Holosun is an enclosed pistol reflex sight. This eliminates the possibility of dirt and other debris from blocking the diode that projects the reticle. Because it is fully enclosed, it must use an attachment plate. Fortunately, there are multiple options, including the 507C mounting plate or the GLOCK MOS mounting plate, depending on the variant you choose. One thing to note is the ACSS variant of the 509 is slightly longer than the 509T from Holosun and is not compatible with the standard 509T plates. 

It’s slightly heavier than the 507C, coming in at 2 ounces. But besides these differences, Holosun’s enclosed ACSS optic is functionally similar to the 507C.   

Holosun ACSS Vulcan Green 

One of the common questions asked by newcomers to mini reflex sights is, “Should I go with a red or green optic?” In all honesty, the best reticle color is the one you like the most. If you prefer red reticles, you should go with red, and the same goes for green. That said, if you’re on the fence about which to go with, we’ve got you covered.  

Red reticle optics tend to cost less than their green counterparts and are generally easier to see in most environments. In bright environments, though, red can be difficult to see and you may have to increase the brightness of the optic to get a better sight picture on your target. For green though, this isn’t always the case.  

Green sits in the middle of the color spectrum. Because of this, it is much easier for your eyes to pick up green against other background colors. Many also perceive green reticles to be brighter than red reticles, even at similar output. Regardless, both colors are more than effective at providing a proper sight picture in a myriad of different scenarios, and it’s ultimately up to personal preference as to which is ‘better’.  

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Holosun 507C and 507K Battery Life 

Both the 507C and 507K from Holosun have incredibly long battery lives. Currently, the 507C mini reflex sight battery can last up to 20,000 hours of continuous running time, which is over two years of constant illumination. The 507K lasts even longer, with a battery life of up to 40,000 hours since it uses a dot reticle instead of a chevron, and a smaller, segmented outer circle thus needing a smaller diode while still being able to use the same battery.  

Tips for Increasing your Battery Life 

Both optics have an auto-off and Shake Awake™ feature, which turns off the optics when they aren’t in use and turns them back on when there is movement. This drastically increases the overall lifespan of the battery.  

Though not always the case, many enthusiasts new to red dots will automatically set their optics at the highest brightness setting. This isn’t efficient for your optic’s battery. To counter this, we recommend trying out different brightness settings to find a balance you prefer. This goes a long way, increasing the battery life of your optic and giving them the potential to last much longer than their continuous running time estimates.  

While the 507K doesn’t have a solar failsafe, the 507C does and has some added benefits because of this. Charging the capacitors in sunlight takes the load off the battery when in use, making it run more efficiently. Even further, the solar failsafe can automatically change the brightness of the reticle depending on the ambient light of the environment you’re in.  

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Mini reflex sights have come an incredibly long way from their beginnings. Where it was once only possible to use a basic dot reticle, there are now a plethora of different reticles to choose from. That said, there’s a fundamental flaw that the ACSS Vulcan Reticle fixes.  

Whether you’re new to running mini reflex sights on pistols or you’re a seasoned enthusiast, being able to bring your sight back to your target when off-center is crucial to making quick, accurate, and repeatable shots. Our ACSS Vulcan Reticle makes this process as easy as possible by eliminating one of the major challenges: finding the center dot.  

If you struggle with finding the center dot on your current optic, or if you’re looking for a more beginner friendly pistol reflex sight, we’re positive that the Holosun ACSS Vulcan sights are some of the best options available. Before buying, be sure to check compatibility charts to confirm that the optic you want will mount onto your pistol, as you may need to purchase an adapter.   

There’s a lot to consider when searching for a good pistol red dot. Consider checking out our guide on what to consider with a pistol red dot and our red dot buyer’s guide to get up to speed on everything you’ll need to know before buying.