A type of Eotech failure that I had not heard of before.


Matt G
September 29, 2007, 03:18 PM
I posted about it here on my blog (http://maypeacebewithyou.blogspot.com/2007/09/and-thats-why-we-practice.html), where you can also read with hilarity how truly I did suck at yesterday's police pistol/carbine match.

Basically, the culprit was the batteries: when exposed to the high heat of a Texas summer in the trunk of my car, the adhesive holding the thin plastic label on the battery (they all wear them now, if you check carefully) melted, and ran to the contact point, where it pooled and created a highly effective insulator. Changing out the batteries did NOT fix the problem.

I completed the match with BUIS, but it's worth checking on, if your electronic sight is ever exposed to high (110 degrees + F.) temperatures.

Be safe.

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September 29, 2007, 03:44 PM
Another reason to go Aimpoint,lol..

September 29, 2007, 06:17 PM
What batteries do Aimpoints use?

Jeff White
September 29, 2007, 06:58 PM
What batteries do Aimpoints use?

Comp M, Comp M2, CompM3 use DL1/3N

Comp M4 uses AA


September 29, 2007, 08:08 PM
yeah, little ones with no wrapper on them. I have a CompML3.. it is the catsass..;) 50,000 hours if u just leave it on setting #7. good till 160 Degrees with no special care or anything to do..;)

September 29, 2007, 08:13 PM
yep that will do it, it took one carbine trainning course before i started using lithium AA bateries instead

September 29, 2007, 10:50 PM
remove the labels and the adhesive?

September 29, 2007, 10:53 PM
That's why (insert chosen diety here) invented open sights

September 30, 2007, 08:51 AM
Were you using alkaline or lithium batteries?

Matt G
September 30, 2007, 09:43 AM
These were N-sized 1.5V alkaline batteries, specifically the Energizer E90. But all tubular batteries use these plastic (mylar, actually) coverings.

"That's why (insert chosen diety here) invented open sights. :neener:"

Uh, peep sights, actually.

Frankly, a very, VERY good solution to dealing with this kind of failure is just to use static ghostring rear sights, which co-witness with your Aimpoint/RedDot/Eotech reticle. Reticle not there? No problem; shoot anyway.

But I'm not really interested in discussing here whether Brand X sight is better than Brand Y sight. I'm pointing out a potential (and real) problem that can and does occur within electronic sights that are fielded by thousands of people.

September 30, 2007, 10:50 AM
Uh, peep sights, actually.

Frankly, a very

Just trying to be funny. Breathe in, breathe out, move on.

Robert Hairless
September 30, 2007, 11:57 AM
Matt, many thanks for that information.

Your opinion, please. I've been leaving the rear sight up at all times, even when the Eotech is on and in use. What I do is focus on the Eotech reticle at those times and ignore the iron sights. When I turn the Eotech off my eye picks up the iron sights and looks through the Eotech. (I hope my explanation is clear.)

So the algorithm is "If see the red reticle, use it instead of what's ahead of and behind it. If not see the red reticle, use what's ahead of and behind it." It's automatic and doesn't require me to think, which I like because I am not good at thinking.

Is my approach okay or not okay? Other informed opinions are welcome too. I grew up with iron sights, not electrical.

September 30, 2007, 12:35 PM
I'll have to play with a couple of batteries when I get home, but would it be (excessively) difficult to remove the labels? Seems to me that removing the labels, then wiping down with naptha, WD40, or other solvent would prevent such problems from arising.

Thanks for posting this, Matt. Corner cases and esoteric failure modes are interesting.

September 30, 2007, 04:12 PM
Interesting, could it be the brand of batteries used? I've run EO's in 130 ambient, more in the sun, without battery labels melting off.

September 30, 2007, 06:07 PM
Last time I took the wrapper off a AA battery (so I'm not sure how applicable it is to an E90) it's just covering up a metal tube and has a dielectric between the tube and one end. So regardless if the manufacturer says not to do it...it's probably ok to take the wrapper off.

Matt G
October 3, 2007, 12:05 AM
Robert, I think it's a good idea for fixed iron sights, but questionable for folding iron sights. Folding sights are, by their nature, a little more fragile than fixed sights. In the up position, I tend to think of them as still more fragile. What you're talking about is "co-witnessing" the two sight systems, though, and that seems to be the absolute best way.

Robert Hairless
October 3, 2007, 12:27 AM
Thank you, Matt. My rear sight is a Troy Folding Battle Sight, which I bought for its toughness. But I just don't have the experience with it to judge that for myself, so I'm happy to benefit from your experience.

Although I've used and owned several other rifles during the past forty years, I suppose my instincts were formed around the M-1 Garand a long time ago and they're hard to break. Each time I pick up an AR-15 my first reaction, for example, is that anything that weighs so little, fires such a small caliber, and doesn't reward me with a nice healthy recoil and loud noise can't be serious. :)

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