A Guide to All the Mounting Footprints for Holosun Red Dot Sights

Whether you’re a practicing gunsmith, an avid AR15 rifle, or a semi-automatic pistol enthusiast, most firearm owners agree that one inevitable thing will happen. During the firearm’s long lifespan, you are likely to swap out the optical system on the upper receiver of your AR15 or the operational action-slide of your pistol.


If this is the first time you decide to make an optical swap, you’ll need to understand the term footprint and the multiple types of mounting requirements. 


These days, there is a tremendous proliferation of quality red dot sights on the market, and although some perform better than others, choosing the right one is still challenging.


However, when polled, many expert gunsmiths will often suggest getting your hands on a Holosun red dot for your pistol, as the Holosun line of sights is historically known for its durability and dependable performance. 


What Is an Optic System Mounting Footprint Anyway

An optic system’s mounting footprint is basically the height, length, and width dimension that the red dot sight will take up or consume after being installed on the pistol or rifle. Another thing to note is that these dimensions are measured in millimeters to ensure a more precise fit of the sight on your firearm. Once you’ve decided to purchase one of the various types of Holosun red dots,

there are a few points you need to remember.  

what is an optic system mounting footprint anyway

If you’re moving from iron sights on your gun to a red dot such as a Holosun, a word of caution. Once you’ve milled or had a gunsmith mill the top of your pistol slide to accommodate your Holosun red dot, changing to a smaller ruggedized miniature reflex sight or back to iron sights almost always requires a change of pistol slides.


Another thing to remember is that different Holosun optic systems may require specific mounting footprints. What’s even more complex is that these same mounting footprints vary depending on the type of pistol or rifle you own. 


Types of Mounting Footprints

The first footprint accommodates Trijicon Type 2 optics, Trijicon SRO reflex sights, and the Holosun 507CX2 red dot optic. Footprint number two typically fits the Sig Sauer Romeo O, a Smith & Wesson Shield RMSc, and a Holosun 507KX2.

types of mounting footprints

As you can see, depending on your choice of Holosun sights, it may require you to choose between footprints numbers one and two to properly mount your choice. It gets complicated because neither footprint categories three nor four typically accommodate a Holosun style red dot optic system.


However, you don’t need to center your purchasing decision on only two of the Holosun styles. As far back as the early seventies, Aimpoint Micro has been a global leader in producing red dot reflex optics and the mounts needed to properly attach them on various pistols and rifles.


Although you’ll want to match the mounting footprints with the Holosun red dot you finally pick, here’s a guide to help you select the correct mount with the suitable footprint.


Holosun 403 and 503 Models


From the Holosun 403B and C models to the Holosun GL and R series of optic systems, Aimpoint Micro offers a unique mounting footprint you’ll need to properly mount the optic system.

Just as there are many unique models of Holosun red dot optic systems, you’ll undoubtedly be able to find the correct mounting footprint at Aimpoint Micro to accommodate your choice. Whether you choose a Holosun 503BU, CU, or C model or a Holosun FL, G, and R model, you can find the proper mounting footprints to accommodate your Holosun 403 or 503 series models. 

Suppose you don’t like being locked in on only one company, such as Aimpoint Micro, to locate the suitable mounting footprint for your firearm. In that case, try many of the various local firearm shops and retailers near you. Many of them stock the correct types you’ll need to help ensure a proper and dependable fit on your gun.  

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Ruggedized Miniature Reflex Mounting Footprint

From the Holosun 503 models to the 507CX2 and 507KX2 red dot optic systems, there’s one thing to understand that will make your pick of Holosun sight a little easier.


Most, if not all, Holosun optic systems such as the 407, 507, and 508 models utilize the RMR mounting footprint. However, the 509 series of Holosun optics may require a unique mounting base to properly mount it.


When purchasing a Holosun optic system, a few letters follow the model number you should be aware of because it makes a difference in the footprint mounting system you need to use. For all Holosun models with the letter C, you’re getting a more prominent RMR sight compatible with the Trijicon RMR mount footprint. However, if you see the letter K – with the noted exception of the 507KX2 – after the model number, this means the housing of the optics is smaller and only compatible with a Shield RMSc type of mounting footprint.


Another way to trim your footprint search is to understand that most of the full-sized RMR Holosun red dots require a similar footprint to the Trijicon RMR. If you finally decide on the Holosun 507C, and your gun already has a Trijicon RMR optic plate on the slide, you won’t need to look further for a mounting footprint. Almost all Holosun’s C model red dots and the Trijicon RMR footprint are the same.


If you intend to equip your pistol with an optic for concealed carry, a smaller housing will probably work better for you. Regardless of which method you choose these models from Holosun and the letters assigned to them will help you select the correct type of mounting footprint. 


Holosun Infinity

Most of this guide has been dedicated to picking the correct mounting footprint for installing your Holosun red dot on a pistol slide.


There are, however, a few red dot optics made by Holosun that are geared toward AR15 rifle owners and Picatinny rails. Each Infinity sight from Holosun comes with a QR or quick release mount explicitly designed for Picatinny rail installation.


Although you may think the Infinity series is a prism scope at first glance, its unique design and appearance fully support a quality red dot optic system. As with all models in the Holosun line, the letters following the model number mean the sight has some specific characteristics. For example, a Holosun Infinity 502 D has elevation and windage controls on the top of the optic instead of a solar panel.


In contrast, the 502 C is solar-powered with an integrated panel on the top of the optic. Holosun offers several models in the Infinity series of scopes. While they all have different combinations of features, you can rely on the fact that an Holosun Infinity is specifically made to install on the Picatinny rail of your rifle.


Whether it’s a pistol or a rifle, a full-sized pistol, or one for concealed carry, Holosun has a full feature red dot optic system for the situation. Your mission will be to understand the type of Holosun red dot you believe will work the best for you and know what kind of mounting footprint your firearm needs to properly mount it.


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8 thoughts on “A Guide to All the Mounting Footprints for Holosun Red Dot Sights”

    • Yes it does. I’ve mounted a 507K X2 to my 590S on the optics ready cut out. The cut out only has two studs where the mounting screws go and the rest of the footprint is flat.


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