Holosun 503G

Holosun 503G

  • Reticle
  • Battery Life
  • Brightness
  • Value
4.3/5Overall Score
  • Battery Type: CR2032 3V Lithium Coin
  • Material: Aluminum - 6061-T6
  • Reticle Color: Red
  • Weight: 4.87 Oz
  • ACSS Reticle
  • Battery Life
  • Price/Value
  • Motion Sensor
  • Factory Mount

The Holosun 503 or the full name of Holosun HS503G is one of the many red dot sight offerings from Holosun but features the Primary Arms ACSS reticle system, a fan favorite here at Lynx Defense.

Primary Arms has included them in the Primary Arms SLx 1x and SLx 3x, which we have reviewed before. We have also taken a deep dive into the Holosun 403B, Holosun HS512C, and the Holosun AEMS.

HS503G ACSS Stock

Holosun HS503G

• Reticle: Primary Arms ACSS
• Battery: CR2032
• Battery Life: 50,000 hrs
• Weight: 4.87 oz
Get the best price: Amazon | Primary Arms | Optics Planet


Battery TypeCR2032 3V Lithium Coin
Brightness10 Settings
Click Value1/2 MOA
FinishHardcoat Anodized
MaterialAluminum – 6061-T6
Night Vision CompatibleYes
ReticleExclusive ACSS CQB
Reticle ColorRed
Optic SizeMicrodots
WarrantyLimited Lifetime
Weight4.87 Oz

Holosun HS503G First Impression

Although Michael has reviewed a few Holosun products in the past, this was the first time I’ve gotten my hands on one of their products. Least to say, I’m impressed. 

I absolutely love the reticle of an EoTech. Although I do have a slight astigmatism, with my contacts or glasses the doughnut of death is still workable.

While over at Michael’s a few months back he handed me a rifle with a circle dot design from Primary Arms and I was blown away by the sharpness and clarity in which I could see the reticle.

There weren’t any blurry smudges or artifacts that I had seen in other red dots and the ring around the dot itself was also crisp and clear.

 At that point, I knew I had to try out one of these new red dots with the EoTech style reticles for myself.

After searching on Primary Arms for a while, I stumbled across the Holosun 503 which was developed in conjunction with Primary Arms ACSS CQB reticle and I was hooked.

I quickly ordered the Holosun and a Strike Industries T1 mount to try out as well. 

Once I received my package from Primary Arms, I immediately opened the Holosun up and threw the battery in to see if it would stack up to my EoTech and the PA circle dot that I had handheld earlier; spoiler alert, it did! 

Holding the unit in hand it felt very solid and the finish felt like it was high quality anodizing.

The glass was clearer than I had been expecting, and the reticle was AMAZING.

The only drawback, if you could even call it that, was the lower ⅓ mount that it shipped with.

Not that it was any less quality than the optic itself, but it was very square and blocky.

Having seen this when I was ordering is one of the reasons I also picked up the Strike Industries mount.

HS503G ACSS Stock

Holosun HS503G

• Reticle: Primary Arms ACSS
• Battery: CR2032
• Battery Life: 50,000 hrs
• Weight: 4.87 oz
Get the best price: Amazon | Primary Arms | Optics Planet


The Holosun 503G showed up at my door quicker than I had anticipated seeing it was around the time of the holidays. 

When I opened the shipping box, I found the Holosun container in a white cardboard sleeve with the name and image of the model printed on the front. 

On one side there were details about the reticle and an explanation on how to activate CQB and Medium range mode.

I found this information very informative, as I would not read any instructions otherwise. 

After sliding the cardboard sleeve off of the container, I noted that it was plastic and had a nice lid.

This was a surprise to me as most of my other budget-minded optics came packaged in cheap cardboard-only boxes.

Things included

Once I had the lid off, the 503G and its included mounts along with the hardware were tucked inside a protectively padded pocket. Also included are the tools for installation and a small container of blue locking compound. 

In my experience, the extras that come along with this red dot are more than many others in the field. 

Holosun HS503G Materials

The Holosun 503G is constructed out of 6061 T6 Aluminum. If you are like me, this info doesn’t mean much at face value. 

After a quick google search, 6061 T6 is a precipitation-hardened aluminum alloy, containing magnesium and silicon as its major alloying elements.

It also has a good strength to weight ratio and is used in lots of engineering applications.


When holding this unit in hand, it feels dense. Not like a brick, but there is some heft to it. It feels like you are getting a quality piece of kit, not a bunch of cheap plastic and pot metal.

The advertised weight for the 503G is 4.87 oz. 

HS503G ACSS Stock

Holosun HS503G

• Reticle: Primary Arms ACSS
• Battery: CR2032
• Battery Life: 50,000 hrs
• Weight: 4.87 oz
Get the best price: Amazon | Primary Arms | Optics Planet


Reticles in red dots have traditionally been really simple; a red dot. Sometimes you may get a green dot, or maybe even the ability to switch between the two.

With the Holosun 503G, this isn’t the case.

Primary Arms ACSS

The combination of Primary Arms’  CQB (Close Quarters Battle) ACSS reticle in the Holosun 503G is an exclusive for this sight. The main issue with red dots is you really have two options.

Holosun 503G ACSS Reticle

The first option is a small red dot, usually one or two MOA that is good for distance but needs a magnifier or its brightness turned way up to be visible during the daylight.

The second option is to use a larger red dot, usually, 5-6 MOA making for better close-quarters battle, but sucks when you need to reach out to 100 yards, and now your dot covers a dinner-sized plate of the target completely. 

Enter the ACSS from Primary Arms. The ACSS uses a chevron, or as some would call it, an upside-down “V”.

This unique design allows for extremely precise shots to be made using the top of the point of the chevron, and quicker snapshots by placing the bottom of the chevron across the torso of the target. 

Taking it a step further, Primary Arms also added in a large horseshoe for quick target acquisition at close ranges and it can also be used to predict a shotgun pattern at around 25 yards.

Looking back to the chevron, you may also use the distance of the top of the chevron to the bottom to compensate for bullet drop. From the tip to the bottom, Primary Arms states that it covers a 100-300 yard drop. 

Looking down from the chevron, you will count three dots. These dots also may be used to compensate for bullet drop. The first dot is 400 yards, the second is 500 yards and the third is 600. 

The Holosun 503G isn’t a one-trick pony. You can switch from CQB mode to a medium-range mode as well. 

This means that you can turn off the large outer horseshoe and retain the bullet drop compensation out to 600 yards. 

This also allows you to make use of the other uses of the chevron. At 300 yards, the width of the chevron is 18”, which also happens to be the distance from shoulder to shoulder on an average man at that distance.

The inside of the “legs” of the chevron show the same 18” center mass at 400 yards.

The dots are one moa which means that at 500 yards, they will cover a 5” circle. 

Knowing all of these will help you get the most out of your Primary Arms CQB ACSS reticle.

HS503G ACSS Stock

Holosun HS503G

• Reticle: Primary Arms ACSS
• Battery: CR2032
• Battery Life: 50,000 hrs
• Weight: 4.87 oz
Get the best price: Amazon | Primary Arms | Optics Planet

Sight Picture

The sight picture when looking through the glass of the 503G is familiar if you’ve ever used a small or micro red dot such as an Aimpoint or any of the other Holosun or Primary Arms offerings. 

The glass quality is really impressive, with only a very slight hue of blue. 

The sharpness of the sight picture is almost as good as looking through much higher-priced options.

With the horseshoe turned on, the sight picture can get busy if you are working at range.

This is why I find it very useful to take advantage of the ability to turn that aspect off when shooting out to range.

For close-in work, the horseshoe paired with the chevron is the bee’s knees. I absolutely LOVE the large ring/horseshoe for up close and personal work.

Eotech got the theory right, but their execution of the hologram left a lot to be desired. Primary Arms and Holosun have fixed the Eotech’s blurry, sloppy looking mess in an impressive way. 

Holosun HS503G Adjustment


To adjust the brightness on the Holosun 503G you will find two rubberized buttons located on the top of the unit. 

Holosun 503G Controls

The forward most of the two has a + on it. Pressing this button will increase the brightness level. The rear button conversely has a -. This will make the dot dim in comparison. 

The brightness settings on the Holosun 503G range from two-night vision modes up to eight other settings.

At the top end, the reticle is so bright that it does not wash out even when viewed outside at full daylight, or when viewed with a 1000 lumen flashlight bouncing back at you off a white wall in my home.


To zero the 503G, the operation is quite familiar to those with other offerings from Holosun.

There are two small capped turrets located near the rear of the unit.

503G Adjustment Turrets

The turret on top once removed adjusts for height, and the turret on the right adjusts from left to right.

The turrets are not captured, but they do feature a notch that can be used to adjust the turrets.

You can also use a flat head screwdriver or the rim of a cartridge. 

Power source

Powering the 503G is a CR2032 3v Lithium coin style battery.

Holosun claims that you will get 50,000 hours of use when using the medium-range setting, and you can expect around 20,000 hours if using the CQB ACSS. 

holosun 503g battery

Along with the impressive battery life, Holosun uses motion-sensing technology to turn the optic off when it sits for extended periods of time, thus stretching that already impressive battery life even further.

When you pick up the Holosun 503G the motion sensor turns the optic on. I’ve not been successful in attempting to bring the optic up to my eye quick enough to witness the optic turning on making it a seamless transition from battery saver to operation.

Holosun HS503G Durability

We don’t currently have a standardized test for durability. This is something that we plan on working on in the future. 

That being said, I feel quite confident in stating that the Holosun 503G can withstand a nasty beating. 

The materials used in the construction of this red dot are high quality and should take some punishment. 

I don’t plan on going to war with this red dot, but being placed on a range rifle hunting setup, plinking gun or perhaps even a self or home defense setup would be a good choice for the 503G.

HS503G ACSS Stock

Holosun HS503G

• Reticle: Primary Arms ACSS
• Battery: CR2032
• Battery Life: 50,000 hrs
• Weight: 4.87 oz
Get the best price: Amazon | Primary Arms | Optics Planet

Mounts and Mounting Options

Like most Holosun optics this optics includes a factory mount.

Factory Supplied Mount

The Holosun 503G comes with two mounts in the box. 

The first mount is a low mount. This mount is used when you have a firearm such as an AK that has a drop to the stock. 

Other firearms that have drop stocks are most shotguns, and almost all rifles besides an AR platform.

The other mount that comes in the box from the factory is a lower ⅓ mount. This mount is a popular height to use on an AR-15, and allows for the use of flip-up or fixed iron sights.

This height allows for the iron sights to be co-witnessed through the glass of the optic. 

The supplied high mount is a little blocky and squared off. I have no complaints about the supplied high mount other than its ascetics. It should hold zero and is a quality part.

Strike Industries T1 Mount

Seeing how I didn’t really care for the way the supplied mount looked, I went ahead and ordered the newly released T1 Riser mount from Strike Industries. 

I know, I cringe a little whenever I see or say that name. Visions of red and blue anodized hand grips, charging handles and hand stops flash through my mind. 

Thankfully, the T1 mount does come in normal black anodization. 

For those of you who like a little color flair on your weapons, fear not. Red is still an option along with FDE and “Titan” which looks like an orangish-yellow to me on a computer screen.

The design of the Strike Industries T1 mount is skeletonized and looks aggressive. I dig the design choice they made. 

Another draw to the Strike Industries mount is that it comes with an insert that covers the two major heights for co-witness on an AR15.

If you like absolute co-witness, then leave the included spacer out.

If you want to run the optic at lower ⅓ height, add in the spacer and use the slightly longer supplied screws to attach the optic through the entire mount. 

After installing the absolute mount and testing it out on my AR, I decided to go with the lower ⅓ height. This choice was made to keep my fat thumb from taking up part of the optical window with my thumb overbore (and pressure pad for my light) grip.

I found that this height was just enough to get the clearance I was needing and still be able to keep a good cheek weld. 

Strike Industries makes the T1 mount from 6061 T6 aluminum, which we covered earlier. The clamp and screw are steel, which is a good choice as these areas receive high stress.

In my opinion, the Strike Industries T1 Mount is good to go! 

HS503G ACSS Stock

Holosun HS503G

• Reticle: Primary Arms ACSS
• Battery: CR2032
• Battery Life: 50,000 hrs
• Weight: 4.87 oz
Get the best price: Amazon | Primary Arms | Optics Planet

Holosun HS503G Application

I see several applications for the Holosun 503G. Simply put, anything that has a 1913 rail that can successfully mount this optic. 

I plan on using the 503G on my home defense AR. As I stated earlier, I am using the Strike Industries T1 Mount in conjunction with a SIG Sauer Juliet 3 Micro magnifier.

The Micro Magnifier allows me to be able to stretch the legs on my 11.5 AR and fully utilize the ACSS reticle that is employed in the 503G.

If I ever tire of using it on the AR, I could also easily see myself placing it on an AK or even a tactical shotgun.


All in all, I am very happy with my purchase. I absolutely love the ACSS reticle design and its sharpness/clarity.

I plan on keeping the 504G on firearms that I either use or handle daily.

I also plan on revisiting this review in the future to give an update over time of how the 503G is holding up to use.

HS503G ACSS Stock

Holosun HS503G

• Reticle: Primary Arms ACSS
• Battery: CR2032
• Battery Life: 50,000 hrs
• Weight: 4.87 oz
Get the best price: Amazon | Primary Arms | Optics Planet
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