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:

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.

Soldier Systems:

Over the past few weeks, three separate issues have come to our attention regarding EOTech’s line of Holographic Weapon Sights (HWS). While we initially thought they weren’t related as they came up one by one, we realized they were all connected once we had looked into all three. Consequently, we believe they should be presented together, along with the source documentation.

Although it’s the last one we uncovered, we’ll begin with the most glaring piece of information. On 14 September, the SOF Weapons Program Management Office at NSWC Crane released a Safety of Use Message regarding issues with EOTech’s Enhanced Combat Optical Sights (ECOS), which is how they refer to HWS. This certainly caught our attention as the PMO is responsible for USSOCOM weapons. That message ultimately serves as the linchpin, tying together the other two issues we’ll soon address.

This critical bit of information would have been a stand-alone article, but it added credence to the others and offered coherence to some otherwise inexplicable issues. It also allowed us to concentrate on the facts presented in the various documentation. We will introduce the other issues after you get a chance to read the SOUM, which was obtained by Soldier Systems Daily. The Message has no date-time-group but was transmitted via official email traffic to SOF units on 14 September, 2015 and there are no markings limiting distribution.

Click to view PDF

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.

Listen to me, EOTech.  Just like we have noted with Remington and the Walker Fire Control System, it would have been better, cheaper and easier for Remington had they noted the problems up front, fixed them, recalled the parts, or refunded the clients.  Instead, the lawyers and corporate executives got involved and things went down hill.  Now, Remington is a shell of what it once was.  And for good reason.  I’ll be surprised if they survive except for government contracts.

Fix the problem.  Come clean about it, explain it, recall it, refund the parts, or do whatever you have to do.  Otherwise, you will lose market share, and permanently so.  You’ve been warned.