Propellants burn at different efficiencies at different temperatures. You will have a different POI if you zero a weapon at 80 degrees and shoot it at 20 degrees. Never heard of laying a cartridge in the sun to make it “hotter”?

I have an EOTech on my Colt and have been pleased with it.
I do not shoot it much so I can't speak on drift in varying temperatures.
Bought an AK earlier last year and have found that I'm better with that rifle than the AR so that's my go to weapon.
I did sight the EOTech in at 40 yards in warmer weather and now my interest is piqued as to whether it does drift in colder weather. Might have to dust her off this weekend and see.
If it fails this test I'll probably scrap the sight and get another or just use the BUIS.

quote:

Originally posted by jezsuiz:
Propellants burn at different efficiencies at different temperatures. You will have a different POI if you zero a weapon at 80 degrees and shoot it at 20 degrees. Never heard of laying a cartridge in the sun to make it “hotter”?

Yes, I have; that was one of those “other” issues I referenced, so thanks for mentioning it.

Changes in propellant temperature, however, have absolutely nothing whatsoever to do with your statement that, “Any sight [emphasis added] will have poa poi shift if the temp changes too much from when the zero was set.” The problems that EOTech had were with the sights themselves, and not point of impact shifts due to changes in propellant temperature. No one would have blamed EOTech for something like that. We might as well say that the inability of a sight to track properly when making windage or elevation adjustments isn’t important because wind and air density differences will affect points of impact to some degree.

So, I’m guessing that the answers to all my questions in my previous post are negative.

I have personally seen it on aimpoints and scopes on hunting rifles. Some it’s as been said just a powder issue, others the sight literally lost or shifted zero. It’s not an uncommon problem whether you choose to believe it or not.

quote:

Originally posted by jezsuiz:
It’s not an uncommon problem whether you choose to believe it or not.

I gave up “choosing” to believe things that were based on nothing more than hearsay and anecdotes with no evidence to back them up long ago. But you evidently have some empirical basis for your beliefs, so I’ll reiterate my questions. It’s been claimed by others that Aimpoints are also subject to zero drift with temperature changes, but I’ve seen nothing more than one or two Internet posts; if it were an independently-established fact, I would expect we’d have seen some EOTech-type outrage, but thus far nothing. And then there’s your prior statement that “any” sight is subject to the problem. How many sights have you seen it happen to, and which ones? How do you know that the POI shifts were due to the sights? Could propellant temperatures or other factors have actually been to blame? Based on your personal experience with Leupold mark 4 and 6 sights, should I expect it with all of mine? If so, how much, and at what temperatures? It hasn’t happened to me yet despite using them in pretty wide environmental conditions from single digits to the 90s, so now I’m curious.

The issues with EOTechs are well documented. You are the only one I have ever heard of that has seen temperatures affect an Aimpoint. And I have seen the zero change on some scopes, but that wasn't due to temperature changes either.