We take a in-depth look at the best red dot sights providing you with detailed reviews on which sight is best for all of your shooting, hunting or tactical needs.

Holosun HS403B Review

It is about time we review the Holosun HS403B Micro Red Dot Sight (MRDS).

Even though it took us a while to get to it, I think you will be surprised to find how much value there is in one of our favorite budget red dot optics for rifle, carbine, and shotgun applications.

This budget-friendly optic has all the necessities and some standard additional technologies you have seen in other Holosun optics.

In the course of this Holosun HS403 review, we outline the specifications along with the features of this wallet-friendly red dot sight.


Plus, we will include a comprehensive look at the technologies Holoson has included in this MRDS.

Finally, we will cover the pros and cons of the optic and what other shooters have to say about the sight.

Perhaps you already have all the information you need and are ready to pull the trigger.

Then go straight to Amazon.com to purchase this feature-rich budget red dot sight.

Click here to purchase the Holosun HS403B Red Dot Sight at Amazon.com.

Holosun HS403B Micro Red Dot Sight Review

The Holosun 403B is a tube-style micro red dot sight machined from lightweight T6 Aluminum. This optic weighs 4.3 ounces measuring  2.44 (in)  x 1.18 (in) x 1.45 (in). Target acquisition is achieved effortlessly through a crystal clear  20mm objective lens and crisp single 2 MOA red dot reticle. The 403B operates on a single CR2032 lithium coin battery providing an estimated 50,000-hour battery life using the mid-brightness setting. Price and quality make the Holosun 403B an excellent red dot sight option for rifle, carbine, and shotgun for the under $200 price range.

Holosun 403B Review mounted

Headquartered in Walnut, California, Established in 2013, Holosun has since built a reputation for building full-featured red dot optics with innovative technologies. Since its foundation, Holosun has continued to add value often at the request of its customer.

Holoson’s 403 line of micro-optical sights consists of several models of budget-friendly options that still incorporate some of the industry’s best features and quality.

Bottom Line Up Front

The Holosun 403B Micro Red Dot Sight carries the same Holosun quality and innovations as its other optics at a budget-friendly price. This optic is suitable for a wide range of applications and is an excellent option at this market price point.

Holosun’s 403 series optics come in several configurations, with the HS403B representing the most straight forward simple design. The optic is easy to put into action with a shallow learning curve.


HS403B mounted on a carbine

Any skill level of shooter can be putting rounds are target within an hour or two with the HS403B sight.

Top Features of The Holosun HS403B Red Dot Sight


The HS403B is a tube-style red dot sight milled from 6061 T6 Aluminum stock. The use of T6 allows for lightweight yet strong housing.

The 403B weighs in at only 4.3 ounces.

This optic is finished with a matte black Micro-arc oxidation (MAO) finish to produce a dense oxide film that protects the aluminum alloy from corrosion attack.

Research shows that the MAO technique has demonstrated greater bonding capabilities than many other aluminum surface treatment techniques.

This ensures a highly resilient coating that resists scratches and protects the aluminum housing for an extended duration.

From a profile perspective, the Holosun Paralow HS403B is on par with other red dot optics in its class.

The sights dimensions are 2.44 (in) x 1.18 (in) x 1.45 (in)  with a 20mm diameter window size providing a compact red dot sight with a more than an adequate field of view necessary for situational awareness and rapid multi-target acquisition situations.

The 403B toutes an Ingress Protection Code of IP67, which means the unit can be dropped into a body of water up to a meter deep for half an hour.

This red dot is also resistant to dust. An IP67 rating makes the optic water-resistant suitable for operation in just about any environment you find yourself.


If you are familiar with Holosun reticles, then you know that most of their optics come with their proprietary multiple Multiple Reticle System. This is not the case with the 403 micro-optical sight series.

Red 2 MOA dot reticle

Holosun’s HS403B comes with a red super led illuminated single 2 MOA dot reticle. The reticle has 12 brightness settings. Ten of those settings are considered daylight settings, with 2 of the settings reserved as night vision compatible.

The range of brightness options ensures that the reticle is observable under various ambient lighting conditions.

Looking for a different reticle color in the Holosun 403 series, then you can check out these other 403 series variants:

Green 2 MOA Dot Reticle

The HE403B-GR is a Holosun Elite series variant of the HS403B with a green super led illuminated single 2 MOA dot reticle.

Holosun’s elite series variant is milled out of a Titanium alloy instead of T6 Aluminum stock and carry the Holosun Elite warranty.

Gold 2 MOA dot reticle

The HE403R-GD is a Holosun Elites series variant of the HS403R with a gold super led illuminated single 2 MOA dot reticle.

The 403R models operate the same as the 403B model except uses a side-mounted rotary switch instead of top-mounted buttons for settings and adjustments.


Battery life for the HS403B red dot sight has been reported in several places as 100k hrs.

We don’t believe that this is realistic since the optic is powered by a single CR2032  3v lithium coin cell type battery.

But, since this is powering a super LED, you are likely to find a 50k hrs battery life while operating the optic on the level 6 or 7 brightness setting.

This is still a fantastic battery life and will ensure that your red dot sight is ready when you need it. 

The Holosun 403B is straightforward to operate.  Turning the sight off/on, adjusting brightness, and other available settings are accomplished with two top-mounted buttons.

Holosun 403B

The Holosun 403 series has a side mount battery tray

To turn on the red down sight, press and release either button. If you need to adjust the brightness, you simply press the “+” or “-” button to the desired intensity.

The default brightness setting for this red dot sight is 7.

To power the sight off,  all you have to do is press both buttons simultaneously.  The sight will remember the last brightness setting before powering down.

If you are not fond of the button style operation of the 403B then Holosun makes the 403R variant.

The 403R models operate the same as the 403B model except uses a side-mounted rotary switch instead of top-mounted buttons for settings and adjustments.

Holosun Shake Awake

The HS403B includes Holosun’s Shake Awake feature. This motion-sensing technology is on by default when you turn on your optic. You can adjust the sleep delay from 0 to 12 hours of no movement for your red dot sight to enter sleep mode.

Once in sleep mode, the sight will instantly wake up and turn to the last setting with the detection of any motion.

This is a great feature that will extend your battery life and keep your sight ready for an engagement at all times.

Sighting adjustments are made via a top-mounted elevation adjustment knob and a side-mounted windage knob.

Screw-on lids protect both adjustment knobs. The maximum adjustment for both the elevation and windage is +- 50 MOA with a 0.5 MOA adjustment per click.


The Holosun Paralow HS403B comes with both a low profile mount and a lower ⅓ co-witness mount.

These mounts are Picatinny rail compatible and use a crossbolt clamp style mounting system. The clamp screw is adjusted using the provided  T10 Torx L-Key wrench.

The low mount is perfect for shotgun applications and carbine setups where no iron sights are present.

For your long rifle applications that require occasional use of iron sights, use the lower ⅓ co-witness riser.

We suggest using a non-permanent thread locker and tightening the clamp screw to 15 in/lbs when mounting.


Included with your purchase:

Need a copy of the HS403B user manual? You can get it here.

Other Great Features of The Holosun 403B

Holosun uses a multilayer reflective glass manufactured using optical glass with multilayer coatings that reduce glare and facilitate maximum light transmission and wear resistance.

Holosun 403b Reticle

The HS403B  has been designed to project its aiming dot to prevent visibility when viewed from the front beyond several meters. This feature reduces shooter signature, which can come in handy under a variety of shooting situations.

This optic comes with the Holosun Limited Lifetime Warranty.

“Your Holosun product is warranted to be free of defects in materials and workmanship with the Holosun Limited Lifetime Warranty. This warranty applies to the first owner upon registration of the product. This warranty specifically applies to the metal structure of the product housing and does not apply to the optical and illumination systems. The optical glass is covered by a 5-year warranty. The illumination system including electronics and LED is covered by a 3-year warranty. Included batteries are not covered under warranty“

A side battery mounting tray allows for easy access when replacing the battery.

Specifications For The HS403B Red Dot Sight


2 MOA Dot only

Brightness Setting

10 DL & 2 NV

Light Source

Super LED



Unlimited Eye Relief


Parallax Free




Battery Type

CR2032 Lithium Coin

Battery Life

50,000 hrs

Adjustment per Click

.5 MOA

Windage Adjustment

±50 MOA

Elevation Adjustment

±50 MOA

Storage Temperature


Working Temperature




Housing Material

T6 Aluminum

Surface Finish

Micro Arc Oxidation

Housing Color

Matte Black

Weight (oz)

2.82 w/battery

Window Size

20mm Diameter

Dimension (in)


Pros vs. Cons of The HS403B

The Pros

Holosun’s 403B carries the quality and toughness associated with other Holosun products. The sights use of high strength aluminum alloy and proven internal electronics will serve a shooter in varying environments.

This red dot sight comes with two different mount options, so you don’t have to purchase additional mount solutions for most applications.

The 403B is priced right, allowing you to put a high-quality optic on your favorite platform for around USD 200.00.

The optic incorporates Holosun Shake Awake technology along with 50k hrs of battery life, ensuring that your optic is ready and illuminated when you need it.

The Cons

The Holosun HS403B doe not come with the Solar Failsafe technology.

If you want an optic with the Holosun Solar Failsafe technology, try the HS403C and HE403C-GR variant, which includes the same features as the 403B but includes the Solar Failsafe feature by moving the operating buttons to the side of the optic.

The Holosun 403 series does not come with the Holosun Multiple Reticle System and only includes a single 2 MOA dot.

Best Place to Buy The Holosun HS403B

We recommend purchasing the Holosun HS403B Micro Red Dot Sight from Amazon.com.  Get a great price and fast shipping! You will also find even more details, ratings, questions, and answers about this red dot sight.

Click here to purchase the Holosun HS403B Micro Red Dot Sight at Amazon.com.

Customer Feedback

The Holosun HS403B  has 4.6/5 stars, 82% of the reviews for this optic at five stars, and over 460 ratings.

Easy to install: Very bright dot, easy to install, easy to adjust, and easy to operate

Battery Life: battery life is bonkers. The battery life is more than you would expect. No disappointments

Value for money: Buy it- It’s a no brainer! I was totally blown away by the quality of this product and at an unbelievable price point.


The Holosun 403 series of optics has several variants around the same price point, so it might be worth looking to get all the features you want.

403B vs 403C vs 403R

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Alternative Red Dot Sights

If you are looking for an alternative to the Holosun 403, we recommend the Sig Sauer Romeo 5. You will get a similar optic with fewer features and a slightly lower price.

Another option at this price point would be the Vortex Crossfire; again, you will get a similar optic with fewer features at a slightly lower price.

Be sure to check our other reviews and guides at reddotsightreviews.com.