In (Small) Defense of EOTech – Thermal Drift in Trijicon MRO


L-3 Communication’s EOTech division is currently going through the PR ringer for the thermal drift found in their (previously) phenomenally popular Holographic Weapon Systems. After USSOCOM released a Safety of Use Message to all its commands (which was leaked publicly) the backlash has been extreme. EOTech has informally recalled all their optics (for full refunds) and

What I have found is that most shooters do not understand that thermal drift is a natural part of firearms and optics. Extreme temperatures cause metal, glass, and electronics to move. Extreme cold contracts metal and extreme heat causes it to expand. This is especially noticeable on thin-walled aluminum optics, which do not have enough material to fully resist the movement. This is all exacerbated by the temperature change on ammunition itself. Cold slows down ammo (dropping groups) and hot makes bullets fly faster.

Reportedsni via Soldier Systems is a statement on Trijicon’s MRO, which also has thermal drift. Going from extremes, this purportedly “high end” optic moves an average of 1.1 MOA, likely not re-setting on the base zero. Basically they are saying that MRO does move and that its “negligible” (depending on your personal standard if 1+ MOA is “negligible.”


Now, I am not saying that one should excuse EOTech, I, for one, do not, as they knew about the issue and did not disclose it, taking a lawsuit from the Federal government and $25.6 Million to settle, but one should not discount the technology as a whole as almost all optics have thermal drift.

So, kids, two lessons:

1.) Thermal drift is across almost all optics. Re-zero if you change climates significantly.

2.) Don’t hide an obvious screw-up. The shooting market has long memories (like Smith & Wesson over the Assault Weapon Ban).

My final hope? That thermal drift becomes a formal specification for optics manufacturers.

Nathan S.

One of TFB’s resident Jarheads, Nathan now works within the firearms industry in weapon design, operations, and sales. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

Nathan can be reached at


  • Lance

    Still buy Trijicon!!!!!!

  • Steve

    I start by saying I have an EXPS3-0 and have zero plans to return it. I’ve had it out in the Winter and Summer in Oregon, and re-zero most rifles annually or better. It’s never given me any cause for concern, as re-zeroing was generally less than a 1 MOA adjustment. Withholding the information was a poor decision, but when you’ve got the kind of capitol L3 does, you can pretty much do whatever the hell you want.

    That out of the way – the excessive thermal drift in the L3 products was basically a design flaw that has been mitigated (whether intentionally or not) by other manufacturers in other ways. As you mentioned, all optics will experience this, but common procedures like potting (encapsulation) and being aware of dissimilar material (or thickness of material) contact can go a LONG way to mitigate this.

    My take on the Trijicon announcement is that they saw the L3 fiasco, didn’t intentionally build their products to withstand extreme temperature swing, and proactively tested it just so they (and their customers) knew what to expect. Now if they’d just address the magnification issue on the MRO… 😉

    • Evan

      EOTech could hardly have handled this thing worse, but I’m still a huge fan of their optics. I’d still take an EOTech over an Aimpoint any day.

      • CommonSense23

        The way they handled this is the biggest issue. The thermal drift while a issue, isn’t the problem that its made out to be.

      • SpartacusKhan

        Why would anyone prefer an EOTech to an Aimpoint? Serious question.

        • Evan

          EOTech is a better piece of equipment in every way besides battery life. Easy target acquisition, good reticle, good field of view, and rugged. Aimpoint is none of those. Aimpoints are basically zero magnification scopes with a massive blurry dot as a reticle. Aimpoints have a tendency to have the battery case come loose with hard usage. If you want to keep an optic on for years, get an Aimpoint. You want a good optic to use, EOTech hands down.

          When I was in the Corps, some guys in my company were issued Aimpoints. Within weeks, they were all at the bottom of their packs and the irons were back on. Aimpoints are junk.

  • Joe Schmo

    Can anyone enlighten me about Smith and Wesson and the Assault Weapon Ban? That was a couple years before my time.

    • Sgt fish

      I know bill ruger supported it. Not sure about s&w

    • Sulaco

      Political rant removed by author. Off topic.

    • sean

      According to Richard Feldman and his book Ricochet it was Colt that did the most damage to our liberties.

    • Short story – when S&W was under different ownership (that being the key in my estimation) they cooperated with the US government/Clinton administration on some issues. Since then, the company changed hands and those folks are no longer running the company.

    • Rusty Shackleford

      S&W were going behind everyones backs and being “proactive” with complying with what anti-gunners wanted. Smith in 2000 were more or less biting the hand that feeds them. Now, the people who made that decision are long gone.

      • J.T.

        Yet apart from a few snubbies, they still insist on having the stupid lock on all of their revolvers.

  • Pseudo

    I’ve already returned my 512 (in December), but I’ve yet to recieve that refund thing they mentioned. Starting to get even more pissed at them. Anyway, my main response to this article is the fury at eotech isn’t that they failed to defeat the laws of physics. It’s that they claimed they did. Of course you’re going to run into issues on any device with thermal expansion and contraction, but it IS conceivable that they came up with some method to compensate and it worked over the specified range. Except it didn’t. Also, the build quality was a known issue and they failed to do anything about it. Honestly, I returned my eotech because the reticle was beginning to fade and no longer went to the edges of the window, a consequence of moisture exposure which it was also supposed to be able to handle. I didn’t use it in extreme temps, so the zero shift wasn’t even that important to me. As an aside, has anyone here actually received a refund from them? How long did it take? I’m starting to get frustrated…

    • Nathan Alred

      Mine went in in mid December, and I’m still waiting. I’ve been told TWICE now that my check is “in next week’s batch to go out.”

    • hughtalkintome

      They confirmed receipt of mine in early January. Crickets. Called two weeks ago and was told it would be issued soon. they said that if I don’t receive it in 3 weeks to call back. Still waiting.

      • Pseudo

        Did you have to call them to get confirmation? I never got anything from them. Shot them an email and never heard back.

    • Kivaari

      I sent my initial request in (via the website) and was advised how to ship the article with copies of the return authorization. It took 2 months, but I got my check in the mail. Just in time to buy Rx medicines.

  • Rusty Shackleford

    AT least Trijicon took the lesson to be learned from EOtech and did their own testing.
    I’m curious if this will lead to more testing of optics for their zero shift.

  • Bill

    Trijicon’s thermal drift isn’t even in the same time zone as EOTECHs. Yes, there’s thermal drift in any optic, ask any amateur astronomer, but Trijicon’s pretty much stays within minute of moron. In good faith, let alone fear of liability, I can’t ride with an optic that could be thrown off in the course of taking it from an air-conditioned Holiday Inn room to a desert gunfight, so I’m still waiting for my EOCheck, while running the original non-drift sights – iron.

  • Shapa

    Regarding S&W and the unholy alliance and capitulation they are asserted to have engaged in times of old when knights were bold and 6.8 wasn’t invented: the interesting thing about it is that I have yet to hear any specifics regarding precisely what it is that they did. I’ve been into the gun game for 15 years now, and have read countless postings from people who swear they will only buy S&W products that were made “before the sell-out.” But I’ve never once read a post where the exact offense(s) were clearly articulated with specificity. The ugly pimple-lock – I get it. But the alleged political product-capitulation remains an absolute mystery to me. If anyone could help this admitted Smith Fanboy better understand precisely what has some people so peeved at former management, I’d appreciate it.

  • VF 77

    Only one question: How much does Aimpoint Micro thermal drift? Is that the reason why you had to say ‘almost all’?

    Dont get me wrong, this wouldnt (and won’t) stop me from buying MRO.

    And the only reason i took the opp to trade in my eotech for pull purchase price was it shut off once under recoil and freaked me out. (And i like lighter red dots now that i’m all growed up)

  • Kivaari

    Remember when EOTech claimed that counterfeits were the optics fiving the failures. It turns out that the counterfeits were simply the sloppy work product of the in-house crew. Did we see fakes or simply bad originals?

    • Sgt fish

      There are a lot of fakes. Very good looking fakes. Go to any third world bazaar or ebay and gun shows and you’ll see plenty

      • CountryBoy

        Yes, even with the L3/Eotech logo on them. Some sites like eBay try to get rid of the fakes, but it’s like playing whack-a-mole as another pops up from China, often the identical item but with a different seller or distributor.

  • Laserbait

    ~2 MOA change for a 240 degree F swing in temp is pretty damn good, in my opinion. I wouldn’t fare as well, I would suspect. 😀

    • FarmerB

      Yeah, if I was going through that change, last thing I would be worried about is a 1 MOA shift in POI. Although, to be fair, it’s VERY easy to get insanely high temperatures if you leave something lying on the ground in a hot, sunny climate.
      Which is why we always left tools in a vertical position (never leave a crowbar and shovel on the ground for instance, unless you want to get badly burnt).
      I once placed a thermometer on the ground at 11am in a hot, arid climate, and it shattered well within a minute). It read up to 212F/100C. Lesson – don’t put your optic on the ground or a metal surface.
      I have an MRO, and I’m very happy with it and don’t care about 1 MOA shift on a 3 MOA SBR VZ.58. In fact, I’m not sure how you can resolve 1 MOA with the reticule in the MRO. Non-issue, but best to come clean on it.

  • Bub

    Makes me wonder about Aimpoints. .?????

  • How does this defend EOTech? Their optics were having a major thermal shift problem, so how does the fact that Trijicons perform a whole heck of a lot better “defend” EOTech?

    You WILL have a POI shift in different temperatures, not necessarily because the optic is experiencing shifts, but because the ammunition’s muzzle velocity is changing with ambient temperature.

    • CommonSense23

      The major issue I see with the Eotech debacle was how the company handled it. If they would have taken a page out of FNs playbook of handling product issues this wouldn’t have been the issue its made out to be.

  • Spencerhut

    And Aimpoint . . . . ? ? ?

  • Marko Ramius

    Date on letter December 2015 and still not on Trijicon website. Make you think why they not publish it. AimPoint, same question.

  • Ian Thorne

    1.1 MOA is negligible to me for a red dot. But EOTech’s had 65+ MOA shifts if I remember right. Not quite the same.

    • Marko Ramius

      Not even close to correct memory.

    • Fred Johnson

      EOTechs have a 65 moa outer reticle ring.

      • Ian Thorne


        I am aware of that, that has no bearing on my statement.

        • Jeff Winters

          “Ian Thorne a day ago
          1.1 MOA is negligible to me for a red dot. But EOTech’s had 65+ MOA shifts if I remember right. Not quite the same.”

          “Ian Thorne 2 hours ago
          I am aware of that, that has no bearing on my statement.”

          Sure it does. The EOTech does not have a 65+ moa shift in zero as you mention. The only thing an EOTech has in common with 65 moa is the reticle ring.

          • Ian Thorne

            No, it doesn’t. Just because two similar numbers are used for different hings does not mean there is a direct connection. That’s not how things work.

            So, then what was the MOA change? Lot’s of people saying no without actually giving other info. Try being actually helpful.

          • Marko Ramius

            Information found on their website:


            The sight has the potential to shift approximately +/- 5 Minutes of Angle (“MOA”) at -40°F and 122°F. Due to thermal drift, the sight may not return to zero. The sights have the potential of approximately a +/- 2 MOA zero shift upon return to ambient (73°F) after being exposed to any temperature between -40°F and 122°F.

          • DaveGinOly

            Jeff is saying that that’s where you got the number “65,” from the diameter of the sight’s ring, not from the amount of drift caused by thermal shift. He’s not saying there’s a “direct connection” between the diameter of the ring and the drift, but that there’s a connection in your mind between a figure from Eotech’s technical specs and the drift.

  • machgman

    3″ to 4″ of thermal drift (diagonal, horizontal, or even vertically) at distances of 50-100 yards during a day when the morning temps are in the 80s-90s F to 120s F in the afternoon heat while in the same general area of operations and elevation is the issue.

    Does the clueless author expects operators to go out and resight their EOTechs EVERYTIME IMMEDIATELY BEFORE EMBARKING ON A MISSION OR DUTY SHIFT???

    Throw in the fact the EOTech had vigorishly and previously denied the possibly of any drift while being fully aware of this point of aim instability and lack of accuracy integrity issue.

    Too bad the author is trying to push a bad and poorly conceived PR effort on behalf of EOTech.

    BTW, unofficial word from USSOCOM is there were no appreciable drift (as documented in the EOTechs) attributed to identical environmental conditions in the identical testing of Trijicon, Meprolight, Aimpoint, Leupold, and other DOD approved to be issued electronic sights. The huge amount of drift and the lack of any consistent accuracy integrity at the short distances the testings were conducted found in the EOTechs prompted USSOCOM to take unprecedented action.

  • RSG

    What are the numbers for Aimpoint? That will be the litmus test to determine the standard. Do they behave similarly, yielding these results as normal? Or do they maintain zero throughout the temp range?

    • Marko Ramius

      AimPoint say no thermal drift but show no test data. Do you believe?

  • HR Pufnstuf

    Filled out the EOTech form on line almost 2 months ago, still waiting on ANY response from them…

  • CavScout

    Calling out S&W over supporting an AWB. What about all the big companies AND your local local gun shops for staying very quiet when they went to ban Chinese imports? So as long as everyone big is on board with it, it’s OK to loose stuff incrimentally?
    Also, EOTech’s leak nitrogen way more than what is acceptable, yet they didn’t fix or disclose that apparently.

  • Dual sport

    “which do not have enough material to fully resist the movement.”

    You are kidding here, right? Metal expands and contracts. This is physics. It happens every day, even with iron sights. It happens with bridges and buildings.

    People often have little understanding of guns and optics and truly believe there is such a thing as perfect when there is not. Gun writers help to perpetuate this myth by using that word often throughout an article.

    The MRO hasn’t been much good since it came out. I saw these going on sale not long after they were released due to many new owners noticing issues right out of the box.