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Holosun HS503 vs HS403 Series | Optics Trade Debates

Hello and welcome to another episode of Optics Trade Debates. We continue on our way through Holosun red dot sights. Today, we’re here to explain the differences between Holosun HS403 red dot devices and HS503 models from 4 different series:

For more information about HS503 and HS403 watch our video

Holosun 403 vs 503

The main difference between the two is in the reticle. The HS403 models have the standard 2 MOA reticle, whereas HS503 models offer the multi-reticle system (MRS). That means that the user can switch between the standard dot and the circle dot (a.i. 65 MOA circle with a 2 MOA dot in the centre).

This switch can be done by holding down one of the brightness intensity buttons for about 5 seconds. 2 MOA equals 6 metres of coverage at 100 metres.

Holosun 403

There are currently 4 Holosun 403 models:

Holosun Paralow HS403C

Holosun 503

As of the end of 2018, there are 5 variants of the Holosun HS503 models and two Elite versions. The standard models are:

  • HS503BU,
  • HS503C,
  • HS503CU,
  • HS503GU and
  • HS503FL.

Holosun Paralow HS503CU
To make this debate more concise, we won’t expand on every single model that we listed.

Holosun HS403A vs HA403B

The HS403A model has its battery compartment beneath the housing and above the mount. So, if you wish to remove or replace the battery, you’ll have to first remove the mount. This is very similar to Docter/Noblex sights. The problem with these models is re-zeroing is needed after each battery replacement. But these models are also cheaper than any other.

All Holosun models that use the letter ‘B’ in the name, like the HS403B, feature a battery tray on the side of the device that can be removed and inserted into the device again.

Holosun Paralow HS403B

There is no HS503B model but there is an HS503BU variant that is the closest counterpart. It has the same battery tray solution as the 403 model, with the addition of the multi-reticle system and it also has shrouded turrets. It’s worth pointing out that there is no model in the 403 family that would come with shrouded turrets, whereas almost half of 503 models feature the letter ‘U’ in their names, denoting that the turrets on those units are additionally protected against bumps and scratches.

The HS403C red dot utilizes the same tray as ‘B’ models but with the addition of a solar panel. The B and C battery compartments are equal in functionality. In both cases, it’s really easy to replace the battery and without losing the zero. The only upgrade that comes with the purchase of HS503C sight is the multi-reticle system. The HS503CU has both the multi-reticle system and the shrouded turrets.

Models that feature the letter ‘G’ or ‘GL’ combination like the HS403GL have a side rotating battery compartment with a cap. HS503G and HS503GU models of the ‘503’ model family are the closest matches. The first one has only the multi-reticle system, while the second one also comes with shrouded turrets.

It’s important to point out that HS403 Holosun models are all mount-compatible with all mounting solutions for Aimpoint Micro models as they use the same profile and recoil stopper on the underside. The HS403A model has a really specific mount that is not compatible with any other red dot.

As far as the mounts are concerned, these models (all, except for the HS403A and HS503FL) come in two different kinds. Each model comes with a high mount for AR platforms and a low mount (about 5 to 6 millimetres in height) for hunting and other applications. The Holosun Paralow HS503FL and HS503G models are the exceptions to the rule as only a low mount is possible with those red dots.


This is everything we had in mind for this debate. Thank you for your attention. Please like and share this video if you found it useful. If you have any questions left, leave them in the comment section below or send us an email and we’ll be happy to answer. Subscribe to our Youtube channel for more content. We’ll see you next time.


Products mentioned:

Holosun Paralow HS403B:
Holosun Paralow HS403C:
Holosun Paralow HS403GL:
Holosun HS503CU:

2 thoughts on “Holosun HS503 vs HS403 Series | Optics Trade Debates”

  1. this would be easy with a chart for the different models with check boxes for what they have or dont have much more simple

  2. “2 MOA equals 6 metres of coverage at 100 metres.” No it doesn’t. I think you mean 65 MOA equals 6 meters of coverage...

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