Combat reflex optics for amateurs – Holosun HS402D

Holosun HS402D red dot

The red dot sight is delivered in a nice padded plastic box that indicates quality contents despite folded hinges. The Holosun Infifniti HS402D is not particularly light, weighing in at 333 grams, which is practically identical to the Aimpoint M4 sight. The price on the other hand is not even near the Aimpoint’s – Holosun being four times cheaper.

Holosun HS402D red dot

Holosun HS402D red dot

Low price – decent quality

However, does cheaper mean cheap? First thing I noticed on the sight was the rust on the lens caps’ hinges. Caps seem to be made of tough material; they are spring loaded and open briskly on tab push. There was also some surface rust on the mounting interface – nothing a couple drops of oil wouldn’t fix but enough to give me a rather poor first impression. A quick attach/detach mounting system grabs a Picatinny (or similar) rail at three sections ensuring good hold. Mount features a lockable eccentric lever and an allen head adjustment bolt which allows for dimensional differences of mounting rails. An insert that sits in one of the rail’s cross cuts, preventing the lateral movement of the sight, is removable and can be adjusted to the non-standard interface if necessary.

Holosun HS402D red dot on the rifle

Holosun HS402D red dot on the rifle

Automatic switch on function

There was no battery delivered with the sight I received which presented no problem since CR2032 lithium cells are quite common these days. It is always good if you can test the sight right from the box therefore the battery should be in its place in the box. With battery inserted the sight will switch itself on at some level of movement. The auto-on function works and by default the auto off is set to eight hours after the sight has been left at rest. This setting can be changed to anything between 1 and 12 hours. As vibration-on is a highly useful feature, it should be better marketed by my opinion (it is merely mentioned somewhere in the manual). The motion sensor switches the red dot on as the sight (or the weapon) is moved or shaken – it sometimes requires a bump to turn it on so it could be more sensitive. The sight can also be switched on with any of the two buttons on the top. The + button increases the dot intensity and – decreases it.

 

Day time bright dot

There are twelve levels of brightness with one extra bright setting, holding the button will not gradually increase or decrease brightness: one push, one level change. I could hardly see the dot on the lowest setting in the darkness and it was clearly visible on a brightly sunlit white background at the brightest setting. This should be adequate for most situations. Brightness is increased with the front button, seems logical; pressing both buttons simultaneously switches the unit off. This does not seem necessary since the battery should be providing enough power to run the sight for 50.000 hours – more than five years, if you can keep switching the sight on after every 12 hours, that is. The dot will always turn on at 7th level of brightness regardless of the previous setting.

Holosun HS402D red dot on the rifle

Holosun HS402D red dot on the rifle

Parallax free optics

There is no noticeable parallax and the dot is well defined and small enough for practical aiming with a Non-magnifying reflex sight (2 MOA declared). Turret caps are tethered to the body and have O-rings for sealing. Adjustments can be made by 1/2 MOA increments (declared) using a screwdriver but I could also use a .223 case rim to turn the setting screws. The battery is located in a drawer just above the mounting lever. This setup does not exactly inspire confidence. The drawer has some kind of O-ring stretched around its base but is quite easily dislodged from its compartment.

Holosun HS402D red dot in water

Holosun HS402D red dot in water

Waterproofness

The device is declared to be protected against ingress of water and dust according to IP67 standard. This means it should be watertight from at least 15 cm to 1 meter of depth. I don’t believe this battery compartment provides sufficient protection against water on immersion (nor washing under tap) but it should stand up to normal use in the rain. I could be wrong though since it was brought to my attention that the sight actually spent five days turned on and submerged in a fish tank at a fair, prior to being sent my way. This would satisfactory explain the rusty hinges and mount (if it wasn’t dried properly) and also the missing battery. If the sight will hold its zero during extended shooting and if the dot stays turned on between shots (battery contacts) the Holosun Infiniti HS402D offers a robust and reasonably priced alternative to some better known brands of reflex sight that are most likely manufactured in the same country if not the same factory.

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