ARMS #40L Question

[doughnut]

I have a question (likely silly) about an ARMS 40L BUIS I recently purchased. It's labled ".75MOA" and has the same plane small and large aperture. Each aperture has a notch on top of it (12 o'clock position). What is the purpose of this? Is it used for reference with the tick marks located on the sight body or is there some other purpose? I've included a poor picture but it illustrates what I'm talking about. Any info would be appreciated. Thanks.

http://img.photobucket.com/albums/v141/doughnut/fun054.jpg

[Parabellum9x19mm]

as i've always understood it, the notch is for short range engagements. i have the same BUIS, but not the SP version.

[doughnut]

Like a notch/post sight picture, that makes sense.

[DocMinster]

I think you guys are right on the money... I have taken a couple Private Civilian Tactical Carbine classes in the past 2 years and one of them had quite a bit Massad Ayoob Lethal Force Institute curriculum incorporated into the class and he explicitly goes over 0-9 meter engagements with the Carbine. And the way I see it as I have a #40 L-P .50 MOA filling this notch with your front sight post would give you precise shot placement at the aforementioned distances.

Doc

[doughnut]

Thanks