Sight Review: Holosun HS503CU Reflex Sight

For more than a few years now, I’ve considered Holosun as a brand that provides a great balance between cost and ability. Offering their customers a product with good overall performance, lots of features whilst remaining relatively modest when it comes to their pricing.

One of the only downsides until now, was the lack of U.K. retailers you could actually buy a Holosun from. My first Holosun came from Hong Kong via eBay, and although my more recent purchase (The HS503G-ACSS) is a somewhat more local purchase (through Sportsman Gun Centre), it’s also sold as part of the Primary Arms catalogue which SGC no longer stock.

The other recent addition to my optic collection, the HS503G-ACSS (to be reviewed in the near future).

When Tactical Kit informed me that they were looking to stock Holosun to complement their existing optic range, I was eager to grab one to add to my collection. As soon as they became available, I had a look through their stock and gave my post-Christmas bank account balance a jolly good seeing to.

What does shopping on Tactical Kit and looking at PornHub have in common? It always starts by opening an incognito window on Google.

The model I purchased was the HS503CU, which might seem like an overly complex name for a red dot sight, but Holosun do have a certain method to their madness. Each letter and number corresponds to a feature offered by the sight, as seen on the below breakdown:

  • HS = Holosun Standard
  • 5 = Multi Reticule System
  • 0 = Standard Accessories
  • 3 = 20mm lens
  • C = Solar Failsafe
  • U = Shielded Turrets

There’s also a nomenclature list on Holosun’s website, which is worth checking out. You might be able to work out which sight is best for you, purely by looking at their model numbering system.

The HS503CU is packaged in a rather nice looking plastic box, a cardboard sleeve fitting over the top and the interior being formed from a pre-cut block of foam. My only criticism would be that the lid doesn’t offer a waterproof seal or even securely close unless you use the cardboard sleeve, meaning that I can’t repurpose it for much else.

The manual does have a couple of errors, “mirco” being one of the few spelling mistakes. The only other errors that I spotted were the mount height being incorrectly listed as “absolute co-witness” (it’s actually lower 1/3 co-witness) and the battery life being listed as 10’000 hours, not the 50’000 listed elsewhere. But considering that even 10’000 hours is over 14 months, it’s hardly important.

The box also holds the accessories included with the sight, which are as follows:

  • Low profile mount
  • Lower 1/3 Co-Witness mount
  • Torx key
  • Spare battery tray
  • Multi-tool
  • Bikini lens cover
  • Lens Cloth

The mounts are basic in their design, the taller one being a lightweight “see-through” block, lacking an independent recoil lug on the bottom and clamping onto the rail via a cross-bolt with a Torx head. The sliding retention block is of a unique shape that’s designed to keep pressure on the rail, working well even on slightly off-spec rails, such as Tokyo Marui’s NGRS replicas.

The anvil shaped cross-bolt block, a clever yet simple design.

The sight is attached to the mount using a short Torx bolt on each corner, this is supplemented with an anti-recoil lug. The mounting design follows the Aimpoint T1 layout, meaning this optic is compatible with the majority of 3rd party mounts out there.

The main body of the sight is made from 6061-T6 Aluminium, machined from billet and finished using a similar technique to anodising called MAO (Micro-Arc Oxidation). This produces a tough, non-reflective and scratch resistant surface.

Windage and Elevation can be adjusted via a pair of dials, both protected by screw-on covers that double up as adjustment tools by flipping them around and inserting them back into the slots on the dials themselves.

Overall, this sight has a distinctively Aimpoint look to it, both turrets are additionally protected with similar shaped buttresses to those used on the T2. The main giveaway at a glance is the large Holosun branding on one side, and the lack of a side mounted battery on the other, but it’s silhouette is certainly more “Aimpoint” than many other red dots.

The shielded windage turrets, they look remarkably close to the Aimpoint T2 design.

Adjustment of both dials is reassuringly stiff, a full 50 MOA (Minute of Angle) of adjustment is available for both Windage and Elevation. The adjustment is made in half MOA increments, this allows you to dial in to a very fine degree. Arguably it’s a little over the top for most applications you’d use a reflex sight for, but as Benjamin Martin once said, “Aim small, Miss small”.

At the top of the sight sits a photovoltaic panel, slightly larger than that used on some earlier models but still not massive by any measure. This panel allows the sight to be powered directly via the power of the sun, in addition to or instead of the 3v CR2032 held within the sight.

The photovoltaic “solar” cell atop the sight enables the sight to harness the power of the sun in outdoor environments.

The objective lens is multi-coated, allowing the reticule to be displayed and to help prevent any reduction of light transmission. This gives it a slightly red finish, which when looking through the sight from the rear translates as a faint blue tint of whatever you’re aiming at.

Looking through the sight, it’s incredibly clear (aside from the mild tint). On full brightness the reticule will flare a touch around the edges in anything other than direct sunlight, but with 12 brightness settings (including 2 NV setting), you can almost always find a brightness suitable for the environment.

Rubberised buttons on the right hand side control the settings, from brightness and auto shut off settings to swapping between solar assisted and battery powered modes. It also allows the user to swap between a dot plus ring or simply use a dot as the reticule. The buttons feature a textured plus and minus, enabling the user to differentiate them in the dark.

The sight uses a CR2032 button cell, housed in a tray beneath the buttons. It is accessed using the included multitool, but a hex key will do the job if lost… Just be careful to not round off the tool or bolts. The tray is water-tight and sealed with an o-ring, essential to the HS503CU’s IP67 water resistant rating, so be sure to look after it and keep it clear of debris when changing the battery.

The “dot and donut” reticule is undeniably one of the main selling points of this particular sight, the layout being a 2 MOA dot sitting within a 65 MOA ring. The addition of hash marks on the horizontal and vertical planes of the ring also assist with minimising unwanted weapon cant and offer additional reference points.

2 MOA is a great size for most peoples requirements, small enough to be very precise over long range (presenting a 1” dot at 100 yards) but large enough that you can easily find it when aiming. Adding the 65 MOA ring makes this process even faster, making sight acquisition almost instinctive.

There are other niche benefits to a dot and ring reticule, hold offs you can learn for shooting at different ranges, it roughly represents a typical buckshot pattern/spread, you can even use it as a makeshift rangefinder. The 65 MOA ring equals 5’5” at 100 yards, maybe not the most accurate way to determine range, but useful nonetheless.

EOTech Tastes, Special Brew Money

When looking through this sight with night vision devices, you can really see how it’s a massive improvement over a simple dot. Keeping track of the aiming point is far easier, even against ever-changing and sporadically lit backgrounds. There is a slight loss in light transmission, but that’s par for the course with red dot sights.

The electronic features are surplus to my requirements for the most part, but they are worthy of mention due to their novelty.

The sight can be set to automatically turn itself off after 10 minutes, 1 hour or 12 hours, this function can also be disabled. If this feature is switched on, you benefit from a “shake awake” ability that means your sight is ready to use at all times, turning itself on as soon as the rifle is moved.

You also have the option of using an “auto” mode, this mode uses the solar panel as its primary source and automatically adjusts the reticule brightness to the ambient light, making up any shortfall with the battery. I find it to be more annoying than useful, and tend to have this disabled as I prefer setting mine up manually (I also don’t use the auto headlights in my car, old fashioned, I know!).

So thats the basics of it, but how does it actually stack up against arguably its biggest competition; Vortex?

I once read that it’s considered lazy in a review to compare one product with a better known one, but in some cases it’s just unavoidable. In a competitive market and with one rival manufacturer being so well known, what makes this optic stand out against it’s often better represented nemesis?

It’s a question that above all others, I’ve been tasked with answering in this review. So whilst I won’t be putting one against the other, I’ll look at the marketplace as a whole when it comes to sub-£300 reflex sights and seeing whether the Holosun HS503CU is worthy of your money.

Holosun’s optics have the edge (in my opinion) when it comes to fit and finish, the MAO coating provides an incredibly tough and durable finish, resistant to all but the heaviest scratches. It feels incredibly well put together, it also offers IP67 certification (not found on some other manufacturers optics) and if I was shooting competitively, Holosun would most likely be my (sub-£300) manufacturer of choice.

Warranty wise, the Holosun comes with limited lifetime cover, which in layman’s terms means that the majority of potential issues that could pop up will be covered, long before you find yourself outside of the warranty.

You would undoubtedly need to jump through a few more hoops than with Vortex if you ever needed to make a claim, but I can only go on personal experience with my HS403C, which keeps on trucking after five years of regular use.

The only thing that isn’t covered at all by Holosun, is accidental damage. But as a friend who spent a rather long time on hot and sandy places once said, “A warranty is worthless when something breaks out in the field, reliability will always beat a warranty”, no one wants to spend the rest of a game day, competition or weekend event nursing a broken optic, in the wild it could be fatal.

My original holosun, the HS403C is still going strong atop the MP7 (note the fitted Guns Modify T1 lens protector)

Accidental damage, certainly within the civilian shooting market is a mostly airsoft specific concern, but a good quality lens protector will keep your optic safe no matter how intense the game gets and should be considered, even for those of you using a Vortex.

Guns Modify make an excellent T1 lens protector that fits many of the Holosun models, however it doesn’t fit this particular one (or the HS503G-ACSS for that matter) unless you take out the rear o-ring and replace it with a thin layer of electrical tape. I am working on a more specific fix, so be sure to keep an eye on my IG feed for more info.

The Guns Modify lens protector, the gold standard of lens protection.

If Holosun suddenly amended their warranty and offered the same level of support as Vortex, I think we’d see a massive surge in popularity (specifically the airsoft market). But I doubt that’ll ever happen… After all, they’ve done well so far and Airsoft is only a very small part of their target audience.

That dark graphite MAO finish, durable and good looking.

So in an ideal world, I’d ask for an idiot-proof warranty (which isn’t essential if looked after properly) and a slightly smaller bezel. That’s hardly a long list of negatives… So the golden question, and one that I’ve been asked a few times over the last few months is; “Why buy this over a Vortex? Actually, why buy this at all?”.

A good quality optic is often the difference between success and failure, it doesn’t matter if it’s Airsoft, Milsim, Range Shooting or Combat.

Everything from training to talent come together to form a sum total of a shooters ability to hit a target, a good quality optic ensures that none of this potential goes to waste. The “poors” love to say that good gear doesn’t make you better, but my rebuttal is that shit kit often makes you worse.

As for the inevitable Holosun/Vortex debate, I honestly struggle to compare both brands with each other. It’s like comparing apples with oranges, they’re both roundish shaped fruit, but that’s where the similarities end.

Vortex trade very much on their VIP warranty (especially within the airsoft market, and who can blame them) and if not being able to look after your sight is a concern, maybe they’re still your best option.

Looking at the physical product alone though, Holosun offers what I (and many others) consider to be a fantastic product, without the compromises found in much of the affordable red dot market.

For those looking for a quality sight at a relatively low cost, the Holosun HS503CU offers a great all-round package. Great battery life, great sight picture, simple controls, rugged, durable and ultimately a third of the price of an Aimpoint.

This sight was purchased from Tactical Kit, who are stocking a comprehensive range of Holosun optics. They’re also the only retailer in the UK (at present) to sell Holosun, with stock available for immediate dispatch.

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