XS same plane aperture > Optics, Mounts, and Sights

Posted: 9/10/2004 10:18:39 AM EDT

This is the XS sight same plane aperture in the LaRue BUIS.
The fit and finish is very good. Groups have same POI at 50 yds with both apertures.

http://homepage.mac.com/mshadwick/imgs/xs_ghost.jpg

http://homepage.mac.com/mshadwick/imgs/xs_small.jpg

Posted: 9/10/2004 11:37:23 AM EDT

[#1]

Very stupid simple question, but how do you replace an aperture on a sight like this?

Scott

Posted: 9/10/2004 12:13:20 PM EDT

[#2]

Yes, how do you change them out?

Posted: 9/10/2004 12:29:05 PM EDT

[#3]

Same way you replace it on any sight. Remove the detent/knob (usually there is a roll pin) then unscrew it from the other side. Takes all of a minute.

Posted: 9/10/2004 1:33:28 PM EDT

[#4]

Quoted:
Very stupid simple question, but how do you replace an aperture on a sight like this?

Scott

The LaRue has a hex screw on the front side.
This little bugger was fixed in place with red thread locker.

http://homepage.mac.com/mshadwick/imgs/xs_hex_screw.jpg

Posted: 9/11/2004 5:32:43 AM EDT

[#5]

Alaskajohn,

I just bought the XS aperature myself. From your pic, it looks like it is installed backwards. Did you do this intentionally? If so, is it because you get a better sight picture? Just curious...

Posted: 9/11/2004 5:54:29 AM EDT

[#6]

I had one and must report that POI did not repeat between the two, there was still windage. You should also know that both apperatures are larger than both A-2 apperatures. Was not worth it for me.

Posted: 9/11/2004 6:53:46 AM EDT

[#7]

Quoted:
Alaskajohn,

I just bought the XS aperature myself. From your pic, it looks like it is installed backwards. Did you do this intentionally? If so, is it because you get a better sight picture? Just curious...

Its backwards. Maybe sharper image? I like mine.-Justin

Posted: 9/11/2004 8:24:23 AM EDT

[#8]

Quoted:
Alaskajohn,

I just bought the XS aperature myself. From your pic, it looks like it is installed backwards. Did you do this intentionally? If so, is it because you get a better sight picture? Just curious...

I simply installed it in the same configuration as the factory aperture. I had no idea it was backwards.

edited to add XS FAQ #9

9) AR-15/M-16 Rear Sight Elevation Shifts And the need for a Same Plane Aperture Sight

As originally designed the AR-15/M-16 sight system adjusts for windage at the rear assembly and for elevation in the front to zero the rifle to the individual shooter. To obtain the ballistic adjustment needed for longer range shooting the original rear sight had one aperture higher than the other. While this system would not give the shooter an exact elevation adjustment for a specific range, it would under battle conditions put the bullet close enough for government work so to speak.

The new A2 rifles and carbines employ a rear sight system that includes a range cam to allow the shooter to more precisely adjust the ballistic arc to their needs. This system eliminated the need for an elevation shift between the large close quarters aperture and the smaller long-range aperture. However the aperture shift is still with us today.

Comparing some of the rear sights available today there appears to be 3 variations available. The 1st style (and oldest) has a .014 offset. This gives a 2.52 inch shift in point of impact at 100 yards between the two apertures. The 2nd style has a .017 offset, which shifts point of impact 3.06 inches at 100 yards. The 3rd style has a .024 offset giving a 4.36 inch shift in P.O.I.

All of the points of impact shifts shown above are for the standard barrel AR-15/M-16 that has a sight radius of 20 inches. The shorter sight radius (14.5 inches) of the M4 carbine and weapons of similar configuration increase the amount of point of impact shift. The shifts for these shorter sight radius weapons are 3.48, 4.25, 5.96 inches respectively.

The only reason for the various shifts would be for changes in the ammunition used by the military over the course of this weapons employment.

Most people are completely unaware of this elevation change that occurs when the aperture is shifted from one to the other. They just figure that their rifle is doing something strange.

Our aperture sight for this weapon has both the large and small apertures on the same plane so there is no difference in the point of impact when you shift from one to the other. We have also offset one of the apertures by .007 to make up for the sideways movement of the aperture on the windage screw as it pivots.

By installing our same plane rear aperture you now can sight in your rifle using the smaller aperture and shift back and forth between the two apertures as your light and range needs change without having to do mental gymnastics to know where your bullets impact will be.

Posted: 9/11/2004 1:12:13 PM EDT

[#9]

Quoted:

Its backwards.

What's backwards?

AlaskaJohn has it right. Small ap. forward when large ghost ring is up.

Posted: 9/11/2004 2:32:17 PM EDT

[#10]

Damn your right. In the pic his apertures look flat. Only the 0-200 on mine are flat. The 300+ is bore through half way to reduce glare or some crap. it still dosent look right for some reason. -Justin

Posted: 9/11/2004 2:36:51 PM EDT

[#11]

Has anyone tried an A1 aperture?

Posted: 9/11/2004 4:14:41 PM EDT

[#12]

Sure. A-1 is for me the best. It is made a bit differently in that the sight seems to be made differently from the A-2. Small apperature is 'backwards' on the A-2. Best sight picture[A-1] for me except in low light. Larger apperature A-2 needed in[fast] low light positions. A true same plane A-2 large[.195] and A-1 combo would get my vote. I was thinking about making up some but perhaps I would be my only, best customer.

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