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Holosun HS503GU Review – the best red dot sight under $250!

Holosun HS503GU is the best red dot sight under $250, It is easy to mount, easy to zero, well adjusted, has 2 different dot settings and is durable.

Reviewed item:

Holosun HS503GU

Editor's rating:

Battery life



Ease of Use


  • Durable and tough
  • Affordable - costs under $250
  • Extensive battery life
  • check
    Adjustment caps protect it well
  • check
    Works well with additional attachments
  • check
    Easy zeroing, click adjustments


  • Brightness is adjusted with buttons instead of a dial
  • Had complaints regarding torx bolt, torx key failing to fit each other well
  • minus
    Manufactured in China

Quick overview

The Holosun HS503GU has red dot sight with two options of either regular dot or circle dot with reticle pattern. Holosun HS503GU most powerful feature is the strong battery life that lasts between 20,000 and 50,000 hours, depending on the brightness levels of the optic. Battery housing, windage and elevation turrets are placed on one side of the Holosun HS503GU. The Holosun HS503GU is only powered by CR2032 battery, unlike the HS503C that is powered by either CR2032 cell or solar cell. It's the best red dot sight you can get under $250. Due to it's low price and product being made in China, there were some complaints about quality of this product, but during our test period we didn't have any quality concerns.

In-depth review of Holosun HS503GU

Here are the qualities that make the Holosun HS503GU gun sight a favourite among gun enthusiasts. 


The Holosun have covered the aspect of red dot extensively by providing two options in their Holosun HS503GU model. The first option is a 65 MOA circle with a 2 MOA dot. MOA is the minute of angle, and two inches are at 200 yards, one inch is at 100 yards and so on. The second option is of a regular 2 MOA dot.

Holosun HS503GU Red Dot

Light Source

The Holosun HS503GU utilizes the LED technology to produce the red dot. The LED light source is powered by a CR2302 battery located on the right side of the HS503GU. It also has 20mm objective lenses and they are designed in such a way that the red dot appears to be located slightly off axis or even tilted. As a result, this angle of lenses enables the light generated from the power source to be reflected back to the sight. The reflected light is seen as the dot that people use as aiming reference. 

This aspect is colloquially referred to as bending of light, which led to the popularity of the red dot. The LED is secured to the inside of the sight tube by using adhesive. The red dot on Holosun HS503GU is also visible even on the lowest brightness level. Thus, as a user, you will still be in a position to aim and follow your target when the brightness level on the dot is low.


Holosun HS503GU is parallax-free. For those of us not familiar with the concept of parallax I will make it simpler in this review. Parallax in optical sight like HS503GU refers to the apparent focal plane of the object on target is offset from the reticle. Normally, both the target and reticle should be aligned on the same focal plane. Parallax will make the object to appear off or on target, depending on how you align your eyes with the optic. As a result, you will end up displacing shots from the target when there is parallax.

Parallax is usually a problem to users with shooting range of over 250 yards. Luckily for us, Holosun HS503GU is parallax-free and you shouldn’t worry about it when using the optic. As a result, this provides eye relief and it becomes easier to set up and lock the target. It effectively reduces the time taken to aim at a target and increases the effectiveness of shots on target, thus, saving ammunition.


Holosun HS503GU is powered by one battery type CR2032. The life battery life of HS503GU is between 20,000 hours and 50,000 hours. From numerous numbers of tests, it has been proven that Holosun HS503GU battery can last for 50,000 hours when the single dot is in use and at mid brightness setting. The battery life decreases to 20,000 hours when the circle dot is used at mid brightness setting. 

Furthermore, the battery life is greatly increased by the auto-on and auto-off features. The auto off is switched after ten minutes of inactivity or no movement, which helps in preserving battery life. The Holosun HS503GU automatically turns on in the slightest movement and it resumes in the same setting it was when it went off. This is another advantage of Holosun HS503GU as it helps in saving time taken to reset the optic.

The battery housing is round with screw-on turrets that make it easy to adjust. It is located on the outside, at the right-side of the optic. This means that you can easily change the battery of the HS503GU, even while it's attached to the rifle.

Holosun HS503GU Attached to Rifle


Holosun HS503GU lens have multi-layer coating. The multi-layer coating is also referred to as antireflective coating, where the inside and outside surfaces of the glasses are coated with a series of layers. This helps minimize the reflection on lenses, consequently improving the clarity of vision as well as protecting the lenses.

Multi-coated lenses are especially useful in night vision. They are also scratch-resistant and repel water or dust. Holosun HS503GU is, therefore, an optic that can be used in extreme weather conditions, and work well in night time. The scratch resistant and water proof lenses make it a long-lasting product.

Temperature testing

The working temperature for the Holosun HS503GU is stated to be between -10C and 50C. The storage temperature for the Holosun HS503GU optic is -40C to 70C. Therefore, the optic can survive in harsh weather conditions and still manage to aim at targets efficiently.

We've tested the sight at -12C and still seen no issues with it's functionality, so you might be able to push beyond their advertised temperatures, but there are no guarantees it would last for long in harsh temperature like that.


The Holosun HS503GU comes with two different mount brackets. This means that you get both hi-rise and regular mount in the Holosun HS503GU case.

Holosun HS503GU Package

The two mounts will enable you to set to co-witness with your iron sheets. The concept of co-witness means that iron sights in your gun will align with the optics. When both optic and the iron sights are aligned, then this is what is referred to as co-witness. The first type of co-witness is the absolute co-witness. During absolute co-witness, the iron sights and red dots are both aligned, because the red dot and iron sights are mounted at the same height. The other type is lower 1/3 co-witness where the red dot is mounted slightly above the iron sights. In this case, you look through the center of the red dot sight and the iron sights appear to be in the lower 1/3 of the picture. When you drop your line of sight to look through the irons, the red dot drops to align with the irons. 

The benefit of absolute co-witness is that there is consistency when switching between irons and optics. This means that the optics is closer to the bore, which makes it easier to sight-in correctly. On the other hand, iron sights may obstruct the sight of the picture at absolute co-witness. In lower 1/3 co-witness, the additional height enables you to see over the fixed sights. The disadvantage of using the lower 1/3 co-witness is that you must raise and lower the sight when switching between irons and the optics.

It is easy to tighten up the Holosun HS503GU mounts and on rifle it takes an average of three minutes. We personaly haven't had any issues with the mounts of Holosun HS503GU and haven't reflected on this within the review, but some people have said that the mounts are terrible as they fail within few days of use. The screws are bound to break after sometime, thereby limiting how well you can use the mounts for sights. Therefore, the mounting base will be loose and the optic will start sliding back and forth. As a result, you cannot aim with such loose optic. But like I've mentioned, this is not an issue we've had personally and can't talk further about the accuracy of those claims.

Sight Operation

It is easy to operate the Holosun HS503GU optic. To power on the sights, you just have to press the + or - buttons that are at the top of the optic. To power off, press the + and – buttons at the same time, which turns motion sensor off as well as the power. The brightness are adjusted using the + and – buttons. Holosun HS503GU has 12 options for brightness settings.

The 7th level is the default setting for the Holosun HS503GU optic. The use of + and – changes the contrast of the red dot against the target. After ten minutes of inactivity, the HS503GU optics will automatically go into sleep time mode. When the motion sensor is on sleep mode, the Holosun HS503GU automatically turns back on with slightest movement at the same settings it was on when powering off. Pressing – button for 3 seconds will enable or disable the circle reticle. This function is useful as it can be used to save battery voltage.

Zero Setting

The top of Holosun HS503GU optic has an elevation adjustment turret, whereas the windage adjustment knob is on the right of the optic. The factory setting for the sight is at zero. The turrets have protective caps that are equipped with built-in screw driver tool. As a result, you just have to open the protective cap, position the slot type screwdriver on slotted screw and rotate the screw.

The rotations are audible and each click has a value of 0.5 MOA. Clockwise adjustment of elevation turret moves the point of impact DOWN. Clockwise adjustment of the windage turret moves the point of impact to the LEFT. Counterclockwise adjustments of the two turrets move the point of impact in the opposite direction. It is important to note that when you feel that the knobs cannot be rotated further, you should stop as this indicates the end of adjustment limit. Adjusting the knob further could lead to damages of the device.

Holosun HS503GU With Attachments

Maintaining Holosun HS503GU

Because the lens, including objective window, are multi-coated, cleaning process should therefore begin with blowing away the dust from the surface. Then, using wet cloth or soft cotton, wipe the lens surface to ensure that it is clean. Use lens cleaner or water to wet the cloth and at no time should you use organic solvents like alcohol. Further, avoid using dry clothes or tissue on the surface of the glass. Opening the internal compartments of the Holosun HS503GU will break the warranty. Holosun supports their clients with repair and other services when the product is within the warranty period.

Extensive list of pros:

  • Holosun HS503GS has long battery life
  • It has auto on and off
  • Equipped with audible adjustment clicks
  • It is durable and tought
  • Has 2 dot settings
  • It has extensive brightness settings
  • Clear optics with no red refractions
  • It is affordable as the sight retails for less than $250
  • Adjustment caps are hard to get off, making it better protected
  • It has -38 to 120 F (-10C to 50C) working temperature
  • It is shock, fog and water proof

Complete list of cons for Holosun HS503GS gun sight:

  • Brightness is adjusted with buttons instead of a dial. This is something a lot of people have complained about, but it wasn't yet addressed by the manufacturer.
  • Product is manufactured in China and a lot of people had comlaints about the quality of mounts specifically.
  • During our testing, torx bolt and torx key didn't fit each other well.

Holosun HS503GS 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
  • Magnification: 1x
  • Parallax: Parallax-free
  • Dot size: 2MOA and 65 MOA Circle with 2 MOA dot (2 different options)
  • 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
  • Surface colour: Black or Flat Dark Earth
  • Housing material: Aluminum
  • Housing Finish MAO Finish
  • Anti-shock and anti-vibration: Yes
  • Waterproof: 1m
  • Compatibility with accessories: Yes. Anti-reflective devices, Kill flash, Magnifiers, Concealed engagement unit. They can be easily screwed in to attach them to the optic device.
  • Compatibility with various rifles: Yes. The spacer can be fitted to the red dot optic tube or removed to fit each given rifle.
  • Storage conditions: store in a dry place between -40 to 158 degrees in Fahrenheit (-40 to 70 in Celsius
  • Working temperature: 14 to 122 degrees in Fahrenheit (-10 to 50 in Celsius)


This Holosun HS503GU optic offers excellent and reliable feature for its price. Other optics offers the same features in the Holosun HS503GU but their prices are very high, therefore it makes Holosun HS503GU the best sight under $250.

The sight is compatible with many guns that range from rifles to pistols as well as many additional attachment. The fact that it comes with an auto-on and auto-off feature makes this optic very effective in conserving energy and power. Furthermore, the two mounting options, lower 1/3 and absolute co-witnesses, allows the user to have varied viewing options.

However, there is one challenge that Holosun HS503GU needs to address for it to be fully embraced in the market. Mounting screw have proved to be a challenge to many users, thereby, this might limit its acceptance in the market. But long battery life, clear and multi-coated lens eliminates any reflections on the sight making the red dot visible even at the lowest brightness point and it's still the best red dot sight you can get for less than $250.

Overall rating: 4.4/5.0 stars

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