Eotech | Cold Weather Distortion | Reticle Fade | Thermal Drift | Parallax Issues

Dear Valued EOTech Customer:

EOTech values your business and is committed to providing you with the highest quality products. Provided below is information on four issues that may affect your EOTech Holographic Weapon Sight (“HWS”). EOTech has not issued a recall of any of its sights, and many of our customers continue to use their sights regularly. EOTech nonetheless wants you to be satisfied and is offering refunds at your option.

Depending on the age of your sight and the ways in which you use it, you might or might not be affected by these issues. Many HWS users experience no issues with their EOTech sights especially if (for example) the sight is used in close-quarter ranges, the target is in the center of the window, or the sight is re-zeroed frequently. We hope the information presented below is helpful.

Eotech Cold Weather Distortion

Cold weather distortion generally does not affect EOTech-branded HWS manufactured after March 2008. The historical issue with cold weather distortion was that the HWS’s aiming dot experienced distortion of size and shape when the sight was exposed to temperatures below 32° F. This became worse as the temperature approached -40° F. It had virtually no effect in warmer temperatures or at the close-quarter ranges where the HWS is typically used, because at those closer distances the distortion would not have a significant effect on the point of impact. Although generally unnoticeable to the naked eye, the distortion existed at colder temperatures.

Impact: Generally none for EOTech-branded sights manufactured after March 2008. For sights manufactured earlier, the sights affected are those used in cold weather for longer range shooting.

Eotech Reticle Fade (Moisture Incursion)

Reticle fade as a result of moisture incursion generally does not affect sights manufactured after July 2014. Even for sights manufactured before that date, the effect may not be substantial. The issue is that atmospheric moisture conditions can lead to the HWS’s reticle fading or eventually disappearing. It typically is noticeable first when the reticle appears to dim at the edges of the sight window. The sight’s age and environmental exposure are factors that accelerate reticle dimming. In many cases, however, this condition can be mitigated by increasing the brightness of the reticle, using the sight’s brightness controls.

Impact: None for any sights manufactured after July 2014. Potentially minimal impact for sights manufactured before that date, depending on the sight’s age and use. Whether your sight will experience reticle fade will depend on the factors discussed above.

Eotech Thermal Drift

EOTech’s sights experience a point of impact shift away from the point of aim when the sight is exposed to a temperature different from the temperature at which the sight was zeroed. After zeroing the sight at or near ambient temperature (73°F), the zero position will shift during operating temperature changes. 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.

This shift results from natural thermal expansion or contraction that is present in various materials as they are heated or cooled, and is greater the more extreme the temperature change. For example, when a sight is zeroed at 70˚ F then acclimated to 50˚ F, less shift will occur. On the other hand, if zeroed at 70˚ F, then acclimated to 0˚ F, more shift occurs. The shift may not be significant to shooters who use their sights at close-quarters ranges. For instance, 5 MOA is a shift of 1.25 inches at 25 yards, and is 5 inches at 100 yards. It also is worth noting that thermal effects are evidenced to varying degrees in common optics, as well as in rifle barrels and ammunition as the environmental conditions change. In all events, to achieve optimum accuracy, the sight zero should be verified whenever the sight is exposed to marked temperature changes, and the sight should be re-zeroed as necessary.

There is no repair currently available to eliminate thermal drift. If your HWS experiences a degree of thermal drift that is unacceptable to you, and re-zeroing does not address the issue to your satisfaction, please contact EOTech, as described below, to obtain a refund of the purchase price.

Impact: The sight’s zero will be affected at varying operating temperatures. This may be minimal for sights used at close-quarter ranges and may be corrected by re-zeroing the sight.

Eotech Parallax

All optics experience varying degrees of parallax depending on use and operating conditions. Parallax is an apparent change in the point of aim resulting from a change in the position of the shooter. EOTech’s sights have little parallax when the reticle is in the center of the viewing window, which is the optimum sighting position and also is the correct place for zeroing the sight. On the other hand, if the user is looking through the sight at the outer edge of the sight window – an off-axis view – the parallax error might be up to 4±3 MOA (or a total of 14 MOA across the viewing window) at 71˚ F (for a sight properly zeroed). In other words, parallax can increase as the user’s view approaches the edge of the EOTech viewing window. To put this possible amount of off-axis error into perspective, 7 MOA equates to 1.75 inches at 25 yards or 7 inches at 100 yards. Viewing through the center of the window achieves the least parallax error. Parallax may increase as temperature changes from 71˚ F. At operating temperature extremes of -40˚ F or 122˚ F, there may be an additional 4 MOA of parallax.

Impact: Virtually none if the shooter is aiming through the center of the sight. Relatively small effect at close-quarter ranges, if the shooter is aiming through the very edge of the sight’s window. As described above, the effect is greater when the shooter is aiming off-center, at longer ranges, or at temperature extremes.

Customer Return Policy
We sincerely appreciate your business and will do our utmost to ensure your satisfaction. If you desire a full refund of your purchase price (plus shipping costs), please let us know by completing the form at www.eotechinc.com/return-authorization-request-form.

If you have any questions, please call our Customer Service Department at (888) 368-4656 or email us at support.eotech@L-3com.com.


The EOTech Team