In Note To EOTech, I mentioned the issue of thermally induced setpoint drift in EOTech holo sights, relying on the post at Soldier Systems.
While there is a great deal of information in the SOUM, two glaring issues stick out. The first is the reliability of the HWS in extreme temperatures, referred to as “Thermal Drift”. The PMO has noted a +/- 4 MOA shift at -40 Deg F and 122 Deg F. Second, is the concern over the claim by EOTech that their HWS are parallax free which was the subject of a previous Safety of Use Message from the same office issued 16 March, 2015. In this case they noted between 4 and 6 MOA parallax error depending on temperature conditions. Despite the PMO working with EOTech to rectify the issues, they still have not been resolved.
I sent my article to EOTech and have yet to hear back. Commenter Lina Inverse said:
Got back a canned but not unresponsive reply to my email asking for repair, replacement or refund early this morning:
Hello [my first name, the Customer Service Manager went to that much trouble],
Thank you for inquiring about your EOTech sight. Thank you for inquiring about your EOTech. EOTech is committed to providing the highest quality products to our customers. The Company continues to work on improving our products and will update you when we have additional information.
Amy Miller, the Media Relations Manager at L-3 Communications, who has lots of pictures holding and firing Evil Black Rifles, is a turkey hunter, was at Vanguard USA for a decade before 6 years at L-3, was reported on September 30th as having left, although her LinkedIn profile hasn’t been updated and I otherwise haven’t been able to confirm it. At the rumor level it’s said the supply of EOTech sights to the US civilian market has dried up.
I also found this gem on their Holographic Weapon Sights Troubleshooting page, Sight Will Not Hold Zero section, after the usual mechanical issues:
EOTech users will often experience a point of impact shift away from the point of aim when the sight is used at a temperature different from the temperature at which the sight was zeroed. The point of aim shift may be greater the more extreme the temperature change. To achieve optimum accuracy, the sight should be re-zeroed whenever the temperature changes from the temperature at which the sight was zeroed.
So a bunch of weaselly silently added or changed admissions, which is better than I remember Remington doing, but they’re obviously not getting out in front of the issue.
This isn’t Amy’s fault or anyone else for that matter. It’s the fault of EOTech management for failing to educate the gun-buying public on simple things. And there is nothing wrong with the EOTech. Let me explain.
Something seemed weird about the article when I went back and thought a bit about it, and I should have done my thinking before hitting publish. Occasionally I screw up. I asked Daniel, who used plenty of weapons sights in the Marines, including night vision, EOTech, scopes for DM rifles, and so on (as well as got certified in the sighting school for Scout Snipers), if thermally induced setpoint drift was a known issue with EOTech holo sights. “Of course. And not only that, you carry your rifle around on hikes and bang it, mounts come loose and things happen. And we shot hundreds of thousands of rounds (recoil impact). We were constantly re-zeroing our weapons.”
While I am a nuclear/mechanical engineer and not an electronics and computer engineer, they make all of us take courses in rival disciplines so that we will be minimally educated know-it-alls on most disciplines. I recalled my course work, as well as what I know from ECEs where I work. When electronics get hot, strange things happen. Pumps can start and stop, and valves can change position without anyone taking action. That’s why you keep electronics cool.
And that’s why you re-zero holo sights. There’s a thermally induced current with diodes, and an EOTech holo sight is a two-wire, PN-junction LED. As for that matter, so is an Aimpoint, and whatever thermally induced setpoint drift there is with an EOTech, there will be with an Aimpoint as well. I don’t have to go into the field to prove the point. I know what’s in the component, and I know that a diode controlling a setpoint will sustain drift with temperature increase. Period. No one has invented a diode that can sustain temperature increase without setpoint drift. It’s impossible for there not to be setpoint drift.
As for EOTech, they need to explain this to their customers. They need to make their literature match reality, and they need to update their web site with salient information. As for those of us who have an EOTech, and I do, as well as a flip-to-side magnifier, we need to understand that our weapons are never maintenance-free. We need to understand them, work them, maintain them, practice with them, and care for them. You don’t do things once. You do them again, and again, and again, and again.
