Holosun HS503GU

The Holosun HS503GU is a two option red dot sight providing either a regular dot or circle dot with a reticle. What stands out with the Holosun HS503GU is their trademark power source life which provides between 20,000 to 50,000 hours, and all this for about $250.

The price factor is most probably due to this sight being manufactured in China, which is OK since they conform to the Holosun standards of performance irrespective of where it is made.

So, with this bit of information, I was asked to review the sight and mainly because of my combat experience in the Middle East that let me play around with many sights over the last three decades.


To provide an orderly review, I decided to split this report into categories and discuss each category individually. At the end of the review, I present my conclusions and then it’s up to you to decide if you want to buy one of these amazing little sights.


The Holosun HS503GU can be split into three distinct categories, and these include:

  • Optics; this includes the reticle, the lenses, eye relief and the parallax.
  • Power Source; this includes the battery and the shake awake
  • The body; this includes the mount, the lenses body and the body performance capabilities
  • Operation; this includes the elevation control, the windage control, the illumination control and the overall performance


The Holosun HS503GU gives you two reticle options to choose from, their 65 MOA circle with a 2 MOA dot, or just the 2 MOA dot. For newbies, an MOA stands for a “minute of angle”, and every 100 yards is measured by 1 inch.


The lens coating is multi-layered and includes an anti-reflection coating as well as abrasion-proof coating and color corrective coatings. The inner and external lens sides are both coated with multiple layers that deliver a crisp, color corrective and fog-free coating that withstands just about every abrasion out there. Night vision is enhanced due to this scratch-free coating layer, and it is designed to repel dust too.

This sight uses a 20mm objective lens that has a slight tilt off-axis, this reflects the LED generated dot to be visible in the sight, and is what is used as the aiming reference. This process is what is called light-bending and is the core of all red dot sights.

The Holosun HS503GU is a parallax-free sight, and this is perfect for those long-distance shots. Now for those of you that don’t understand what parallax actually means, here is a quick review.

The parallax is a difference in the apparent position of an object viewed along two different lines of sight. This difference is measured by the angle or semi-angle of inclination between those two lines.

To make it understandable, the human eyes are positioned differently in our head, and as we look through a scope or sight, we view things from different angles simultaneously.

The brain translates this difference and creates a depth estimation of the view we are looking at.

A parallax-free sight doesn’t use this process, is simply applies a single plane of reference which means it’s a straight line of one angle vision, making those long-distance shots much easier to solve.


In terms of eye relief, this optic delivers an exceptional experience, so you don’t get bug-eyed watching targets for a long time, as well as making it easy to acquire a target from zero. The window size is 20mm.

Power Source

The Holosun HS503GU uses a small LED diode to produce the red dot, and this is powered by a single cell CR2032 battery that integrates their shake awake technology to save on power when not in use.

The shake awake technology is a simple motion detector switch that disconnects the power source when the sight is motionless for ten minutes. Then, when the sight senses motion, it starts up again.

This shake awake technology extends battery life to the extreme. Essentially you get between 20,000 to 50,000 hours of illumination from one single cell CR2032 battery. The lower battery life of 20,000 is when you use the mid brightness setting more than the lower brightness settings.


The Holosun HS503GU is made from 6061 aluminum with a black anodized (MAO) finish. What this means is that the surface of the aluminum has undergone an oxidization treatment that provides you with protection against natural oxidization.

Aluminum doesn’t rust, but it can produce a white oxide powder coating. To prevent this, the sight is anodized.


The Holosun HS503GU has two different mount brackets; a hi-rise and a regular mount. These both come in the package you buy. What these two mounts provide are the following:

  • Both will enable you to co-witness the gun/rifle sight with your red dot. You need to make sure your red dot and your gun/rifle sight are at the same height to assure a perfect co-witness. Once these two are aligned, you get that perfect alignment shot. For a one-third co-witness, you would mount your red dot above your gun/rifle sight, and that would make the gun/rifle sight appear under the red dot in the lower third of the picture. This one-third co-witness option provides you with a clearer picture since the gun/rifle sight doesn’t obscure the target, and with small targets that can be an issue. However, with this in mind, the disadvantage of a lower co-witness is that you need to constantly raise and lower your sight when switching between the gun/rifle sight and the red dot.
  • In terms of mounts, they are both easy to use. Both mounts take about three minutes to configure, and I have never come across a Holosun mount issue before. There are some considerations to take into account, and these include securing the mount before you leave for the range. Do not rely on your mount screws to remain tight after handling a load of recoil, so be sure to secure them after your day and also before you go out. Never over tighten the screws, they are delicate little things, and you can cause them to crack if you over tighten them. This is the same for all optics. The central height is 1.63”.

The working environment for this kind of scope is quite diverse, and you can use this model in temperature ranges between -10C and 50C, while you can store it in a wider temperature range of -40C to 70C. This model is IP67 rated, which means you can submerge it in water. These operating temperatures and conditions enable you to use it in harsh wintery conditions, as well as hot dry conditions, as well as in wet and humid environments.

Due to the build, this sight will withstand vibrations and shocks of up to 1000g, which means it can withstand your recoil over and over again.

The body dimensions are 2.44” x 1.18” x 1.45”, and it weighs 6.3 ounces.


Once mounted, the Holosun HS503GU is an easy optic to use. The basics are on and off; press the “+” and “–“ buttons simultaneously to turn it on and off. This also activates the shake awake technology.

To adjust the brightness, you depress either the “+” or the “–“ button, where you have 10 daylight brightness settings and 2-night vision (NV) settings.

When you get this sight for the first time, the default brightness setting is set to number 7, so by adjusting your brightness (contrast) you will either dim or brighten it against the target. The auto mode turns your optic off after 1- minutes of no motion, and will reactivate when it feels a motion.


Selecting between reticles is simple, just press the “–“ button for 3 seconds, and your reticle will change.

The elevation adjustment is at the top of the body, and the windage adjustment is on the right side. The elevation and windage adjustments are simple knobs that come with a protective cap that has its own adjustment tool built into it.

To make an adjustment you need to take off the protective cap, and then turn it over, insert the tool into the slit and turn the knob.

Each turn is a click, and you can hear these clicks. Each click is 0.5 MOA.

Turning the elevation turret to the right (clockwise) moves the point of impact downwards, and moving the windage turret to the right (clockwise) will move your point of impact to the left.

Just take heed when your knob stops moving or resists movement, do not force it, it has reached the end of its thread. If you force it you will break it.


Summary of Features

Let’s take a quick glance at the basic features in tabular form, and is a useful reference guide for its specifications.

Device dimensions:2.6" × 2.5" × 1.3" (66 x 64 x 37 mm)
Weight of sight and battery: 4.87 ounces (138g)
Optical principle:Light Emitting Diode (LED)
Eye relief:Unlimited
Dot size:2MOA or 65 MOA Circle with 2 MOA dot
Settings for brightness:10 Daylight, 2 Night Vision
Battery:CR2032 works for up to 20,000h with circle dot and 50,000 with single dot
Housing material:Aluminum (Anodized Black or Earth color Finish)
Anti-shock and anti-vibration:Yes
Waterproof:Submersible up to 1m
Working temperature:14 to 122 degrees in Fahrenheit (-10 to 50 in Celsius)


OK, so now I reviewed the technical aspects of this sight, how does it work in the field?

To start off with, this optic sits well on a wide range of guns and rifles, and at the price it comes in, is a very strong competitor for top position, with this in mind, I took it to the range and tested it comprehensively.

In terms of mounting the device, it was really three minutes, I mounted it a few times to check my timing, and I did not rush it. Transporting it mounted did not diminish the mounting screws hold, but I did give them a once over at the range, I always do this irrespective of the sight or scope I use, this is like checking your tires before you go into a race.

man and HOLOSUN HS503GU

The next thing is to align it, and you always need to do this once at the beginning. Once you have aligned it, you don’t need to do it again since it’s already aligned. However, never rely on anything but your own wits, so when you do take it out again, check the alignment, that’s like checking your rear-view mirror to see its in the right place before you drive off.

Now I pumped off a couple of shots to see how I acquired the target, and then let loose with over 200 hundred rounds of ammo using a standard AR-15 to get impact, recoil, vibration and even threw the gun over a fence to see how the scope fared with a fall. Then I dragged it through a muddy water trough, took aim and shot. After shooting practice was over, I went home and stored the gun in my gun safe.

The bottom line is that this sight can handle most pressures of the hunt, it’s an easy to use model, easy to maintain the model and for the price you pay, it’s a perfect solution for quick hunting trips and the such. Do not confuse this with a combat-ready sight, it is not designed for combat, it is a hunters sight and a perfectly priced one for civilian use.

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