Previous Post
Next Post


A few months ago I stumbled upon Holosun Technologies, a company out of Florida that makes a range of red dot optics. Nearly all of them employ a solar panel to provide power to the ultra-efficient LED, with a battery backup if it’s too dark. With this combination, the CR2032 battery’s life is up to 50,000 hours (5.7 years). Most of Holosun’s models are available with a 2 MOA red dot only, or like my PARALOW HS503C here with that same red dot inside of a 65 MOA circle and the option to turn the circle on or off. Let’s dive in to check out the rest of the features . . .

In The Box

Many of Holosun’s models appear to come with both low and high mounts. Some of the nicer ones have a good looking quick release mount, but mine uses a standard cross bolt to clamp to any Picatinny or Weaver rail.


Also in the box is the required Torx wrench for the mounts, two battery trays, a CR2032 battery, a handy tool for the small screws that hold the battery tray to the sight, and a good, to-the-point owner’s manual. Oh, and a rubber bikini-style lens cover for this model, while some others have attached flip-up covers.


Perhaps the best feature of most of the Holosun lineup is that you don’t actually have to worry about or do anything. Well, once you have it sighted in, that is. After that and for each time you go to use it, there’s no setup, no adjusting, no configuration. Heck, there isn’t even an on/off button.

Reticle brightness is adjusted automatically thanks to a light sensor somewhere in the solar panel. If there’s enough light to run the LED completely from of the panel — and it doesn’t take much — the optic simply stays on. If it’s dark enough that battery power is being used, the sight powers itself down after a few hours and will wake up automatically with a little light or via a push on one of the buttons. Some of Holosun’s models have a motion sensor and wake up when they’re moved, but my HS503C isn’t quite that fancy.

Brightness adjusted automatically.

The above describes automatic mode, in which the reticle will auto-adjust for brightness and, on this model, will always be the circle + dot. By holding the + adjustment button down for a couple of seconds, the optic will switch into manual mode. In this mode the user can switch between circle dot and dot only, and has full control over the reticle’s brightness. There are 9 daytime settings and 2 night vision-compatible settings.

Mid-range in the brightness settings on a slightly overcast day.

Adjusting windage and elevation is similar to many other red dots. Simply unscrew the turret covers, and click adjust to move point of impact as needed. The bar on the top of each cover fits into the slot on either turret and facilitates easy rotation, and the undersides of the covers are marked so you know in which direction to turn.


The clicks are easy to hear and feel, and each one affects 0.5 MOA of downrange adjustment.

On The Range

My first HS503C unit unfortunately had a defect, and the rear lens wasn’t installed properly and fell out. The sight still worked normally, actually, but it obviously wasn’t waterproof with the lens missing and dirt and debris could get in there and block the LED. The replacement, which arrived rapidly from Holosun with a return shipping label for the broken one [ostensibly] so their engineers can check it out, plus Holosun’s apologies and assurances that this was the first time they’ve seen it happen in over 50,000 units, has had no such issue.

It has now ridden atop my AR-15 for around 1,000 rounds, 500 of which were fired in one sitting as part of the SLF-15 Polymer Lower Receiver review. It also saw a box of .308 while adorning the Century Arms C308 during testing. Primarily, though, it has lived on my CZ Scorpion Evo 3 and works perfectly on that rifle with the low mount, even bottom 1/3 co-witnessing with the factory sights.


The auto mode has been spot-on. Reticle brightness is always correct as long as the target and I are similarly lit, which is where any auto-brightness will break down (e.g. I’m in dark shade so the reticle is dim, but the target is in full sun) and, of course, where the manual adjust mode comes in handy. However, I never actually had to switch it over to manual while out shooting.

I find the circle dot quick and intuitive, and I definitely prefer a fine red dot like the 2 MOA one Holosun appears to use in all of its optics. It allows for more precise aiming than a fat dot, and the brightness capability is more than enough that I don’t think anything is lost in terms of quick acquisition as compared to a larger dot. Plus, the 65 MOA circle with partial crosshairs further draws the eye to the hit zone.

The reticle is nice and crisp. Extremely sharp and clean, in fact, getting only a bit fuzzy on the edges at the very brightest setting or two. Eye relief is effectively unlimited, and the optic really is parallax free at any distance more than maybe 15 or so yards. What that means, of course, is that your eye doesn’t actually have to be centered with the optic for the reticle to be on target. Move your head around and the dot moves as well, going off center in the optic so it’s always right on top of the exact same spot downrange (this is shown pretty well in the video). This, of course, is common to basically all red dot and reflex sights and the Holosun is no exception.


Windage and elevation adjustment were true and the HS503C held its zero for me with no issues. I didn’t really torture test it other than shooting ~1,000 rounds of 5.56, 20 rounds of .308, and a few hundred rounds of 9mm through the blowback-operated Scorpion with it. And, although I’ve taken to tossing optics in their retail boxes down the basement staircase, Holosun #2 took that route as well as the laundry chute. It’s waterproof rated to 1 meter and working temperature rated from 14°F to 122°F, but none of this was put to the test other than shooting it in full sunlight on a 105° day. It did fine, of course.


I think Holosun is offering a lot for the money. The going rate for the HS503C is about $239.95. Some of the models look extraordinarily similar to models sold under at least one other brand name (Holosun may manufacture those), however the addition of the solar panel, the automatic brightness adjustment, and the circle dot reticle option set it apart.

The loose lens was concerning, but the new unit has been fine. The optical system does have a 5-year warranty. Clarity of the reticle rivals that of the most expensive red dots out there, and I think if I could make any one change it would have been springing for an even nicer model. I’d like the quick release mount since I’ve been swapping this thing between firearms a fair bit, and I’d prefer the flip-up lens covers. But then again, the HS503C is smaller, lighter, and less expensive.

Specifications: Holosun PARALOW HS503C Circle Dot Sight

Red Dot Size: 2 MOA Dot; 65 MOA Circle
Eye Relief: Unlimited
Magnification: 1x (zero magnification whatsoever)
Zero Adjustment: 0.5 MOA elevation and windage
Power: Primarily solar-powered with CR2032 battery backup
Battery Life: 20,000 hours for circle dot at mid brightness. 50,000 hours for dot only at mid brightness.
Housing Material: 6061-T6 aluminum
Operation: 11 brightness settings. Automatic or manual, push-button adjust. Circle dot or dot only reticle.
Mount: High and Low riser mounts included
Dimensions: 133x54x72 mm
Weight: 120 grams (4.23 oz)
MSRP: $282.34 (street price ~$239.95)

Ratings (out of five stars):

Build Quality * * * *
Being a little bit generous and assuming that loose lens truly was a complete fluke, the Holosun is otherwise very nice. Clean machining, flawless anodizing and lens coating, perfect and precise fit of all parts including the mounts, good button feel and turret adjustment feel, and it holds zero.

Optical Clarity * * * *
Just about as clear and bright through the optic as around it. I’ve played with a lot of sub-$100 red dots and reflex sights and this is a star above the vast majority of those for sure.

Adjustment & Controls * * * *
Automatic mode is going to suit you just perfectly a good 95% of the time. Doesn’t get easier than that. Switching to manual mode and using the adjustment buttons is simple, and the buttons are sleeker than a large dial.

Overall * * * *
Solid features and quality, particularly the reticle’s sharpness and the extreme battery life, at a price that’s half that of the battle-ready competition. Sure, if I’m actually going into battle or otherwise making a living with my firearm I might spend the extra few hundred dollars, but for any sort of recreational use — even rough use — and possible defensive use the Holosun should continue to serve admirably. Well, maybe not the first one I got but apparently every other one on earth, and certainly my replacement unit.

Previous Post
Next Post


  1. I for one am quite happy to see the proliferation of so many low cost decent quality optics on the market. I’d still recommend going upmarket for a serious social purposes gun, but springing for an Aimpoint for every gun in the safe can break the bank pretty quick.

    If the only use a gun is ever going to see is on the range I don’t see why you wouldn’t save your money and get something like this, especially given that the battery life code seems to have been cracked and low-to-midrange optics can now offer multi-year life from a single battery.

    • No thank you.

      I’ve bought a couple different optics from Amazon that were listed as “new.” One, the box had clearly been opened; the other had the box sealed well but the optic itself showed a lot of wear and tear.

      Amazon gracefully took each return; and granted these were “sold by X, processed through Amazon,” but still.

      From now on I’m only buying optics from places that specialize in optics, firearms gear, or both.

      • Interesting, I’ve been buying a lot of stuff from Amazon. Bought a UTG BugBuster and it was perfect, it did come directly from Amazon.

      • What does that have to do with this optic? The situation you described can happen with ANY product on Amazon. But it from Holosun’s affair if you’ve got an issue with Amazon. Pro tip from someone who buys everything off of Amazon, don’t buy products with only a free ratings, and don’t buy from sellers with <1000 reviews, 95%+ which are positive.

  2. This looks like a great offering for lower cost red dots. I recently bought a Black Spider red dot for around 150 and it has been great for the price point. Put it on my frankengun AR and have around 500 rounds through it so far in one sitting.

      • It appears as though it’s no secret so I’ll confirm that Holosun does manufacture some of the Primary Arms-branded red dot optics. I don’t believe there’s a PA-branded one with the solar panel, circle dot, or automatic brightness adjustment though, so they’ve stuck to the couple of Holosun models that are simpler in function and also a tad smaller & lighter (compatible with Aimpoint T1 mounts) than the HS503C that I’ve picked up.

        • Actually, PA has recently announced that they’ll be selling one with the solar battery (I’m not sure which exact model it is, though). It was on their Facebook.

    • Shhhhh. Bro. Dang.

      …I’m sure I’ve achieved compliance for the purposes of these photos by removing the requisite 5 foreign-made parts. There might be a trigger visible there, but obviously the FCG is empty inside and the magazine follower is a piece of scrap plastic and the muzzle device has been removed, etc…

      CZ still says it’s just barely on track to release that 922(r) compliance kit “by the end of summer.” And technically that means before the 23rd of this month…

      • I manufactured* replacement parts for mine.

        * According to the ATF, when they stopped processing Washington SBR Form 1 paperwork, adding an engraving to an existing firearm is “manufacturing” a new one, so I “manufactured” new parts by polishing the old ones.

        • If it worked that way then 922(r) wouldn’t apply to Form 1 SBRs. But it does*. Under the law you may have taken a pistol and “manufactured” it into a rifle, but it’s still a foreign import under 922(r).

          * I realize there is online debate about this, but the 922(r) law clearly does apply to NFA items (and has since the GCA of 1968) and the ATF has clarified this point repeatedly, citing relevant Federal code, etc. Additionally, CZ-USA spent some resources on the subject and begrudgingly (as it directly hurts their sales) did determine that a compliance kit is necessary for owners wanting to turn their Scorpion Evo pistols into SBRs. Relevant parts need to be made in the U.S., and slightly modifying the imported parts doesn’t cut the mustard.

        • I think the argument is that all the parts are “manufactured” in the US the second you give them a good polishing. Therefore, while the pistol would still be an “import”, it would contain 0 “foreign manufactured” parts.

        • I get the argument. I thought of doing that myself (modifying the existing parts). But, as mentioned, it doesn’t appear to meet the legal requirements. Or, if it does, you’d have to win a court battle against the ATF, which has stated repeatedly that they believe it to be in violation of the law, which I infer means they’d prosecute accordingly. Again, corporations with lawyers have determined the same thing, which is why many go through the large expense of manufacturing or buying replacement parts instead of doing the much, much simpler and cheaper modifying of the original ones. If a little polishing or the drilling of a 1/32″ drainage hole in the relevant parts made them “U.S.-made” then that’s what manufacturers would have always done.

          The whole thing is absurd… don’t get me wrong… but I’m not interested in being some sort of test case. I’m waiting for compliance parts and, apparently, we’re almost there in the case of the Scorpion Evo…

  3. I’ll be honest, the lens thing freaks me out a bit. If that had happened on my T-1 or EOTech, I’d be pissed. OTOH, I’ve always wanted a compact sight with an EOTech style dot and halo system. Now the question comes down if I want to sink $250 into an unproven technology.

    • If it happened to an Aimpoint or EOTech we’d think “sh*t happens” and know it was a fluke because of the rep of those companies. In this case, it’s harder to say. If their statement that they had never before seen it in 50k units is true, then there you go. But obviously I have no way of verifying that.

      I wouldn’t exactly call it unproven technology at least in that it operates on the same system as most of these things, just with the addition of a solar panel. They’ve been around in the U.S. for a couple years, the Primary Arms-branded ones have earned a very solid reputation, and they’ve been in use in other countries I think a decent amount more than in the U.S. so far. I even saw a photo of Ukrainian fighters (not sure if Army or what) with Holosuns on their AKs…

      • I’m actually concerned about the brightness feedback and power sharing circuits. That adds more “fiddly bits” to the board that can go bad. (Not to mention that Chinese made solar cells have a poor reputation.) I’d almost rather have one without the solar panel just for the simplicity.

      • I would also prefer the IP rating to be a bit higher. IP67 is not a very high rating and does not require the electronic components to be resin backfilled. IP-68K would be much better for something like this. (A high standard, given the other players in the market, but given the extra “fiddly bits” might be a necessity.)

        • Unfortunately, as I teach my students, IP67 is a very specific test that’s not really applicable to most real life situations. It’s a short duration, static immersion test at fairly low pressures. That means that the seals don’t have to have the same integrity as a 69K test. (The 69K test specifies steam entry, not just liquid water.) Interestingly enough, I have seen water get into a 67 rated device with intact seals. It comes in as steam and then condenses on the inside.

    • Not really unproven. I have had a Holosun Red Dot (NON Solar) for 3+ years and at least 5000 rounds and I have not yet put a new battery in it!! Mine does have a slight red reflection that can be seen in certain lighting conditions (it was a problem with early Holosun’s) but it is only a slight distraction. I love mine and it is a lot lighter than than my Aimpoint M4’s.

  4. I would be lying if I said I wasn’t interested. Reticle options and a deceint battery life. My only qualm with it is that it is already half way to an aimpoint pro or exps2. Sure it offers a little bit of both, but I am just concerned for what I would be sacrificing. Mainly a range toy but I still would want to be able to use it for HD or be rough with it if it came down to it. Guess I could always buy and worst case scenario put it on one of my less used systems. Thanks for bringing this product up Jeremy.

    • yeah thats very true I hadn’t thought of that. It is nearly halfway to an Aimpoint Pro and it might benefit to just go with the tried and true. Never the less, the expansion of cheaper optics technology benefits us all.

      • I guess y’all are “glass half full” types, then 😛 . Because it’s either “already almost halfway there” so you may as well just spend twice as much, or it’s “not even quite halfway there” so it’s a whole ‘nother ballgame.

        • Yeah that is another way of thinking about it, but I can’t really talk I have an even less expensive optic riding on my Frankengun.

        • Yeah, my go-to red dot before this one has been a sub-$100 Bushnell TRS-25. It’s great. But I really like the auto-brightness of this Holosun, I like the crazy battery life, and I like the finer, 2 MOA dot. The reticle is also crisper with sharper edges and such. And I didn’t need to buy a separate riser to get it to co-witness on an AR.

        • trs-25 on the rws48, the boy’s charger takedown and a .44mag deagle. not sure if that last one will hold up.
          2moa would be preferable to the trs’s 3moa dot.

  5. Unfortunately, that looks like the sort of red dot that flares and bleeds really badly because of my astigmatism.

  6. That nub on the top of the turret cover for adjusting is pure genius! I am very interested in this ‘lil feller.

    • Aim point has beed doing the same thing for years. My T-1 has the exact same setup. (Admittedly at 2x-3x the price.)

      • It’s been around since before Aimpoint, too. Back in the day I had some sub-$25 reflex sights and red dots that did the same thing. Actually, some of them didn’t have turret caps at all but came with a separate adjustment tool, and it would have a similar “key” for showing which way to turn and you placed the tool on top of the turret (or adjuster set screw) to turn it…

  7. Jeremy how would you rate this against something like a strikefire or sparc2? They’re both a few less $$ than this holosun

  8. Holosun also has some less expensive offerings. I have one of the older 2 moa dot only with no auto adjust that I bought for $165. It has an auto wake feature so I don’t ever have to touch it, which is pretty good for a night gun too. It has kept zero on my 12 gauge without an issue.

  9. Would not recommend holosun. I put 100rds through one of their less fancy dots on a 5.56 AR and it did not hold zero. They’re sending me a new one, but I’ll be selling it – I’d much rather trust a Primary Arms for budget defensive use.

    • Be sure to do your homework on any Primary Arms red dots because Holosun manufactures quite a few of Primary Arms’ red dots without the Holosun logo.

      My cheaper red dot from Holosun didn’t lose zero on my 12 gauge, so I have confidence in them, but ymmv.

  10. I bought the HS515c version of this unit
    with 2 MOA its a no brainer
    best dot for the money anywhere

    I will be picking up a few more

  11. I noticed in the video the gasket is sticking out of the edge of the battery tray if you use a little silicone grease on the gasket it won’t do that it’ll slide into the hole properly.

  12. My rear glass fell out, too. I had only fired 5 rounds or so and was doing reload drills when it fell out! Also, I let them know it fell out and received a replacement. It can’t be trusted though.

    • What model was it that the glass fell out of? How does the glass fall out with a retaining ring holding it in. I own 4 of these (one 503c and 3 515s) and see no way the glass could just fall out unless nothing was holding the retaining ring in. I have read nowhere else of the rear glass falling out of these optics or PA ones.

  13. i got to use one of these on a friends cz scorpion last week and it was sweet. it looks like they dont make the 503c anymore. is there a newer version?

Comments are closed.