Holosun 507K X2 with the ACSS Vuclan Dot

Holosun's 507K is a solid pistol mountable dot for slimline pistols. Primary Arms's ACSS Vulcan reticle offers some solid advantages. The combination results in a very enticing optic that is worth a deeper look.

As some of you know and like many of you, I’m not a stranger to the Holosun 507K X2. In fact, I’m a fan of the 507K. It is arguably my favorite micro pistol mountable dot that I find to pair exceptionally well with slim line pistols like the Glock 48 and Sig Sauer P365 XL. I’ve grown very fond of Holosun’s multi-reticle system which when configured with the ring only has been aptly dubbed the “doughnut of death”. Its large size lends itself to be easy to find and easy to use at fast rates of fire. Given the 507K is also a very durable dot, it is a red dot sight I very often suggest for defensive carry use on slimline pistols.

Some of y’all might be wondering, why am I bothering to write yet another review on the 507K? Especially since I’ve reviewed it in the past and it’s a relatively well known and commonly used optic. Well, this variant I got my hands on is a tab bit different and there is a little story behind it.

It all started about a week ago when my buddy at Primary Arms called to see how my holidays went and what my plans were for this year. We got to talking about some of the optics I reviewed for them last year which led to a fair amount of banter regarding my experiences with the ACSS Vulcan reticle on the 507C he sent me last year. It was at that point that he offered to send me this 507K which has an ACSS Vulcan reticle. It’s not the exact same reticle, and I’ll get to some of the differences shortly.

Before I keep going and for transparency’s sake, I want to disclose that I am affiliated with Primary Arms and therefore have a monetary relationship with them. That means that I may receive a small commission should a purchase be made on the Primary Arms website after using a link found on this blog or that I’ve shared on social media, email, or other communication medium. Additionally, they sent me this optic free of charge for testing and evaluation purposes. With that out of the way, let’s continue with the review.

There is nothing different about this 507K other than the reticle, some branding on the right side of the housing and the box packaging, and the addition of a reticle manual in the box contents. Everything else is identical. So for the sake of brevity I will leave out the physical description and refer those who are interested in those details to read the review on the 507K published on this blog about a year ago.

The ACSS Vulcan Dot reticle is composed of a 3 MOA center dot which is the aiming reference and 230 MOA dashed outer ring that encircles the center dot. When the pistol is presented at full extension and aligned with the target, only the 3 MOA dot is visible (unlike the picture above where the camera was only a few inches away from the optic). When the pistol is presented at full extension and misaligned with the target, then a part of outer circle will be visible and provide a reference of alignment correction which should be faster than the typical “waving around” that most folks do in order to find the dot.

A couple of things here. When aiming and there is no reticle or dot in the window, “waving” the pistol around to find the reticle or dot is a waste of time. Instead one should immediately switch to using the iron sights, which is why I’ve become very fond of having backup irons on a pistol with a mounted optic. Having nothing in the window is more often the result of human error than the result of an optic failure. Nevertheless, switching to the irons is something that has to be practiced and trained. It’s a skill that requires development as is practicing presenting a pistol so that it is properly aligned with the target when the presentation (or transition) is complete.

This brings us to a point of contention regarding the ACSS Vulcan reticle. Some folks argue that having well developed pistol handling skills makes the outer ring component of this reticle useless and having it will make people lazy because they will rely on the ring as a crutch for underdeveloped skills. I understand the argument and the sentiment. However the reality is while I would love for every pistol owner to devote time to acquire a high level of proficiency, most won’t. Those who have the drive and resources to improve their proficiency will do so regardless if the “crutch” is present. With that in mind, I find the reticle design to provide value to a very large audience. Let’s explore that a bit.

Folks who won’t or can’t, for whatever reasons, improve their proficiency can benefit from the alignment correction reference any time they use their pistol. This will lead to less frustration in recreational activities and could make all the difference in successfully defending themselves in a self defense scenario.

For folks who are new to dots, the reticle design can serve as a training aid to help develop their presentation or transitions with a pistol mounted optic. Their progress can be tested by running drills with the outer circle turned off (which can be toggled on and off by pressing and holding the decrease illumination button found on the left side of the optic for 3 seconds).

For folks who have already developed a high level of skill, the “crutch” can be used for rapid alignment correction in those rare events where human error rears its ugly head. Stress and duress have a way making all of us more prone to human error.

It’s probably pretty obvious that I like the reticle design a lot. However, there is one thing that I would change. It’s not a huge deal, but I would prefer a larger center dot. This is personal preference based on what I have found works well for me for the pistol shooting activities I frequently participate in. I find that the larger my aiming reference is, up to a point, the faster I can run the pistol while still maintaining an acceptable level of accuracy. I’m on the fence as to whether or not this preference will result in me switching back to the “doughnut of death” over the ACSS Vulcan reticle. Time and experience will be the judge. For the time being, I’ve slapped this 507K on the P365 XL and will give it a fair shake before finalizing any decisions. There is a lot I like about this ACSS Vulcan reticle (which is also available in green) and I think if it would have had the 10 MOA center chevron that is found in the ACSS Vulcan reticle available in the 507C then a permanent switch would be pretty much a sure thing.


  1. Very cool. I didn’t realize Primary Arms was offering this. I love my 507K although I’m thinking of swapping it for an EPS Carry . . . assuming I can ever get one.

  2. Nice review. As a 507C acss user, I agree that PA ‘missed the mark’ with their long-awaited K version.

    The use of PA’s chevron (over even a 10MOA dot) would have provided the benefits of a 1MOA dot at the tip PLUS the quick acquisition of the standard 507K’s 35MOA circle dot useful in most rapid close encounters.

    Yes the 230MOA ring may help find the dot for new optics shooters (or those who like the advantages of off-hand, panicked and awkward body positioning); but honestly, with these small K series windows, if you’re even looking through it at all, then you can find the 35MOA circle of the standard 507K which is also sold for le$$.

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