Odd Question About DD 1.5 Rear Sight

[Jellybean]

So a relative of mine just finished putting together an AR.
He is using the Daniel Defense 1.5 fixed rear sight (the complete upper is basically a DD V3 config) .

When we were sighting it in the other day I noticed an odd thing happening.
I zeroed it at 50 yds using the small aperture. We both hit the same with the small aperture.
However, as he wears glasses we decided to try the large aperture to see if that would help any. This is when I noticed we were both making hits in completely different directions.
Now when I looked on DD's website it didn't say otherwise so I'm assuming this is not a same-plane aperture sight, so that would account for the space difference, but not the direction difference.

What I mean is when I shoot with the large aperture (vs the small ap) I hit high. When he uses the large aperture he hits low. Seeing as how we both hit almost the same with the small Ap, this caused quite a bit of confusion during initial zeroing....:o

Any idea what is going on here?

My initial thoughts are
A) we're simply getting different sight pictures, or
B) maybe his glasses are causing him to see it differently (although I would think this would be the same with the small ap if so).

We were able to compare with two other ARs- one had the same 1.5sight, and the other had an MBUS- same results (for him) with both.

Honestly, I'm stumped, and seeing as how everything else seems to be working fine I'd probably write it off as situation A, but due to some hiccups in procuring this upper, he thinks something may be defective, so for my own peace of mind....

[Guns-up.50]

Well I think you may have answered your own question. If it were me I would say you guys are getting differnt sight pictures. With the larger apt there is obviously more room for error. If you want try to BZO the rifle w/ small apt at 25yrds your impacts should be about 2 inches lower than your aiming point, this sould get you on paper @ 100 yrds
Hope this helps and good luck

[DBR]

For IBZ you want to be dead on at 50yds with the small aperture. This is about 1 1/4" low at 25yds.

[Guns-up.50]

For IBZ you want to be dead on at 50yds with the small aperture. This is about 1 1/4" low at 25yds.

I guess i dont see the real point of Zeroing the rifle at 50 meters seems kinda pointless? The 2 inch @ 25 meters id the distance between the sight post and center of bore.

[fdxpilot]

I guess i dont see the real point of Zeroing the rifle at 50 meters seems kinda pointless? The 2 inch @ 25 meters id the distance between the sight post and center of bore.

Actually, the 50yd zero is becoming very popular because POI will be within 2 1/2 in of POA all the way out to over 250yds, which covers most of the normal shooting folks do with an AR15. A 25M zero will be about 10 1/2 in above point of aim at 250m. That's way to big a hold under for me. With a 50yd zero, you just point and shoot. See Molon's thread on Zeroing the AR15.

http://m4carbine.net/showthread.php?t=65679

[Guns-up.50]

[QUOTE=fdxpilot;1210261]Actually, the 50yd zero is becoming very popular because POI will be within 2 1/2 in of POA all the way out to over 250yds, which covers most of the normal shooting folks do with an AR15. A 25M zero will be about 10 1/2 in above point of aim at 250m. That's way to big a hold under for me. With a 50yd zero, you just point and shoot. See Molon's thread on Zeroing the AR15.
QUOTE]

Thanks for the input I have never seen this before. I like what I see, I am still used to the USMC standards 36m =360m ect. So the way I see it is once zeroed @50M the rifle is set +/- 2.5 inches out to 250M?

[markm]

Forget the big app.... It's a complete crapshoot. I've never been able to hit anything with that thing.

Small app is where your money should be.

[Jellybean]

Thanks guys!
That's about what I thought.

[crowkiller]

Here is an option to convert it to same plane if that is what he wanted.

http://www.midwayusa.com/product/610584/dpms-ashley-ghost-ring-aperture-ar-15-a1-or-a2-steel-matte

[Axcelea]

If the small aperture is set for a 25/300 then the large should be more the 50/200, if not in the same plain. There should be an experienced drop in POI from switching from the small to the large. I would guess it is just differing sight pictures.