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. 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.

    The above post is my opinion and does not reflect the views of any company or organization.