I just got a #40, and am getting ready to mount it.

Question:

I understand the large aperature is for 250yd and the small one is for 500yd.  Now, how are you supposed to use the 'notch' on top of the 500 yd sight?  And what do you use the 'horizon line' for?

Regards,

Jeremy

I have wondered the same thing about the "horizon" line.

I just figured arms just cut the top off the sight so that
it would be flush when the sight is folded down.

On the arms with the standard A2 sights, the small aperature
sticks up alittle when the sight is folded down.

Ditch the original Aperture and put a stock one in your 40. That's what I did... the Horizon line is gay and just a marketing tool  to cover the fact they needed to shave it flat so it would not stick up when folded.

And how many 500-Meter shots is a guy gonna make with  BUIS on a 5.56m....


Don't waste you energy putting a lot of thought in to it..... replace and enjoy

Thanks for clearing that up Harv.

How did you go about replacing the aperature?

Regards,

JO

Drift the Pin out of the side of the adjustment wheel and unscrew it out until the Aperture can be removed. Replace with a full size uncut Aperture and reverse the process. It's pretty simple ( I can do it..)

I have no concrete proof as to why they did it, Just my Opinion based on owning it and looking at the design of it.
What other logical reason would any designer have to take a rear sight aperture and cut it in half.

What would you call a "Horizon" line?? if not a Marketing tool....

We are still entitled to have our opinions.....or did I miss the memo on that one............

What is the “horizon line”  used for anyways? Celestial navigation?

Never mind, found it.

A.R.M.S. #40 STAND ALONE FLIP UP REAR SIGHT 500-600 METERS The A.R.M.S.® Stand Alone Flip-up sight, utilizes the same well proven concept as the rear sight on the SWAN® Sleeve system. The unique design of the spring loaded rear sight, ensures constant battery action and repeat zero. The sight is held in the locked down position by a quick release lever, that prevents the sight from being accidentally engaged, but is as fast as a trigger to release even with arctic mittens. The initial elevation zero utilizes the standard M16/M4 front sight bead. When the sight is released into battery the 250-300 meter aperture is ready for immediate close combat use. For longer ranges the leaf sight aperture is rotated to access the 500-600capability with the built in horizon line feature that helps lead distant targets and lets the shooter square the rifle to counter windage offsets, if the rifle is inadvertently tilted. Other type rear iron fold-down sights require the shooter to push it into position, which means they can be accidentally knocked down at the worst time. The A.R.M.S. spring loaded flip-up sights never let you down, because they're designed to always be there even when going thru brush or being dropped.

I agree with you that the cut is there for clearance and that is it's sole purpose. Where I believe the marketing comes into play is the fact that their are no Instructions on how to use this great feature that was Engineered for the sole purpose of assisting in lead corrections and to help prevent cant......

Anyone see the Instructions ?????? I must of missed them.  Advertising a feature with out instructing the user as to how that feature works is a marketing ploy in my book.

If it was milled simply for the purpose of allowing an ACOG to fit over it (which I believe it was) then why the extra added sales pitch for this "Horizon " line...


I will add in my future post's that it is just my opinion as I Agree with you whole heartily that I need to back up a statement like that with facts and I do not want to mislead others.....my bad....