I zeroed my EOTech early in the day and it was as dead on as it could be (read not a great group, maybe a 6" group, but center was dead in the bull, even on all sides, 10 full mags).

I went back and shot again later after dinner, and it was high and left (read center of this group was 6" away from the bull at 11:00). Both groups done at 25 yards.

As I understand it there are never any parallax issues, so wtf? Base is tight, it feels so good on the rifle, but something is obviously wrong here...

Any thoughts?

How hot was your barrel when you zeroed the gun?  If it was really hot from shooting 10 full mags, you would probably notice a POI shift from a cold barrel.

Did you use different ammo??  were you prone, sitting kneeling???

Try to zero it again, if the problem still exists, call EOTech and see if there is anything they can do to correct the problem.  

One out side of the topic point, you should always sight your red dot at 50 yards, it gives the best and the flatest shots out to 250-300 yards.  check out the IBZ on the Maryland shooter web site.

[url]http://groups.msn.com/TheMarylandAR15ShootersSite/zeroingmethods.msnw[/url]

Before to zero yr EOtech did you already zeroed yr iron sight ?

What's the group with the iron sight @ 50 meters ?

A close mate of mine had same troubles zeroing his ACOG but the troubles were in the rifle not in the TA01

PP out

CavVet

Bench the rifle, shoot your group, see how it is.  THEN, have another shooter try it.  You may have been tired, but 6" off zero is a big difference at 25 yards.

I would also rezero just on general principles.  6" at 25 yards is not acceptable for a zeroing target IMHO.