Cowitness height above bore question (AR15)

[Coronach]

I finally got a LaRue mount for my Aimpoint, and it is slightly elevated to allow lower 1/3rd cowitness. I'm going to be headed out soon to rezero the optic, and I suddenly wondered, is my sight height above bore considered to be different?

I ask because I was looking at the different ballistics tables, and tweaking sight height (of course) makes a difference. I was going to do the 50/200 IBZ0 regardless, so in many ways it doesn't matter, but I was curious what it would do to my shot placement within the IBZ0. If the value is considered to be something other than 2.6, what is it?

Thanks,

Mike

 

[rob_s]

If you have access, zero it at 50, then fine tune at 200, then recheck at 50.

 

[Coronach]

I do. That's my plan. I was just wondering if anyone knew for sure what the proper height above bore was considered to be in this instance.

I know that this ain't x-ring shooting, though, so it probably doesn't matter.

Mike

 

[taliv]

2.6 + lens diameter*(1/2 - 1/3) ?

 

[Coronach]

So, you think, 2.6" + 1/6th the lens' diameter? Hmm...I'll have to get out my ruler.

Mike

 

[RyanM]

In theory, the height should be the exact middle of the scope.

If you want to be really precise, you can also figure out the exact distance that the scope projects the dot at (I think usually around 50 feet), and use that as your sight radius. Even Aimpoints aren't parallax "free," it's just the error introduced past the projection distance is less than the size of the dot.