Using your BUIS and Aimpoint's T2 optic

[Unobtanium]

I have tested this at 25 and 50 yards. At 50 yards, I get a 2" shift. At 25 yards, I get a 1" shift.

When shooting with irons, looking THROUGH the T2, POI is shifted up and to the left. When shooting with the T2 optic removed, it is shifted down and to the right.

It is a consistent 4 MOA shift, in my testing. I tested with different ammo, and on different days. The results were always the same.

This is something to be aware of. Zero and shoot accordingly.
http://i62.tinypic.com/288oxte.jpg

[GJM]

Just an issue with a T2, or T1/T2, or Aimpoint generally, or all RDS?

[Unobtanium]

Just an issue with a T2, or T1/T2, or Aimpoint generally, or all RDS?

I have only tested this extensively with the T2. I think it may have to do with the "extreme" cant of the front lens of the T2, which Aimpoint uses to better focus the dot. I cannot, however, say that other RDS/AP's do not also do it. I have not checked.

[MSparks909]

Interesting...I'm running a T2 in a 1/3 DD mount with DD backup irons on my 16" middy. I zeroed my BUIS prior to mounting the T2. Next time I go to the range I'm going to check zero and adjust accordingly. Thanks for the heads up.

[GJM]

maybe we need these:

http://www.laruetactical.com/troy-offset-sight-set-front-and-round-rear

[Chuck Haggard]

I always zero the irons and then instal the sight, never took the time to see if the glass would bring a significant zero shift or not, my plan being if for some odd reason I had to make a longer shot with the BUIS due to the dot being dead that I would use that handy quick detach feature built into the mount.

[breakingtime91]

I always zero the irons and then instal the sight, never took the time to see if the glass would bring a significant zero shift or not, my plan being if for some odd reason I had to make a longer shot with the BUIS due to the dot being dead that I would use that handy quick detach feature built into the mount.

my thoughts as well..

[Unobtanium]

I always zero the irons and then instal the sight, never took the time to see if the glass would bring a significant zero shift or not, my plan being if for some odd reason I had to make a longer shot with the BUIS due to the dot being dead that I would use that handy quick detach feature built into the mount.

I agree, but should someone want to take a longer shot without removing the optic, they would need to have zeroed with the optic in place for optimal results.

[Beat Trash]

I agree with Chuck about just removing the optic.

But you have my curiosity aroused.

This is something I have never actually checked out. All my Aimpoints are T-1's and PRO's. While I like the T-2, I don't dislike my T-1's enough to sell them off and replace with T-2's.

Next time I'm at the range, I'll shoot irons one one of my guns, with and without the T-1 installed.

I'm curious to see what happens.

[GJM]

But you have my curiosity aroused.

This is something I have never actually checked out. All my Aimpoints are T-1's and PRO's. While I like the T-2, I don't dislike my T-1's enough to sell them off and replace with T-2's.

Next time I'm at the range, I'll shoot irons one one of my guns, with and without the T-1 installed.

I'm curious to see what happens.

Me, too. I have noted the POI windage shift between large and small aperture, which was a surprise, but never a T1/2 effect on BUIS zero.

[Unobtanium]

Me, too. I have noted the POI windage shift between large and small aperture, which was a surprise, but never a T1/2 effect on BUIS zero.
Some irons do not have an offset machined into their apertures I have found.

[Luke]

Some irons do not have an offset machined into their apertures I have found.

What does this mean?

[GJM]

Unobtainable, out of curiosity, did you notice this shift with the large aperture, small aperture or both, and what model/brand BUIS?

Wannabe, in the Troy BUIS at least, we notice windage shifts going from large to small aperture. This minute, I am forgetting which way the shift was. We noticed it when my wife was zeroing Troy BUIS on a AAC .300, and she shoots good enough groups to clearly see it at 50 yards. (I just use the small aperture.)

[Unobtanium]

Rosh works sl1 up front and magpul MBUS rear. Small aperture only.

[Unobtanium]

What does this mean?

Many BUIS dual aperture flip on a screw. Screw has threads. The rest is simple math.

[SLG]

I have not tried this with my T2's yet, but with T1's and Comps, I have never seen this kind of shift. I usually zero my irons without my RDS on, and then shoot them through the RDS during training.