When I attended an Appleseed shoot back in 2014, I was frustrated with the whole zeroing process. It wasn’t anything Appleseed did, but more the settings of the standard 6/3 carry handle sight I was using at the time.
You see, I was accustomed to practicing iron sight shooting at 100 meters and the Appleseed event took place at 25 meters. The 6/3 sight was never designed to easily accommodate both settings.
You could either zero it at 25 as intended, and use the elevation markings, or set it for 100 meters and not use the elevation wheel.
The RIBZ sight setting, short for Revised Improved Battlesight Zero, helps with that.
The Carry Handle
You’re supposed to zero the 6/3 carry handle at 300 meters. That also happens to correspond to around 36 meters. This works since the intersection of the sight line and bullet trajectory at 36 meters is below the bullet’s maximum ordinate. The trajectory of the bullet will continue to rise, and then begin to fall.
It intersects the sight line again around 300 meters.
Military practice is zeroing the 6/3 sight for 300 meters. Since that is significantly below a 100-meter point of impact (POI), the elevation drum bottoms out well before you can raise the POI high enough.
The military intended for all personnel to use the 36m/300m zero and then swap to the larger 0-2 aperture for fighting. The underlying concept here is called the Point Blank Zero.
The Zeroing Problem
The standard 0-2 aperture is on a different plane than the smaller unmarked sight. Specifically, it’s 2.5 MOA lower. When the unmarked sight is set for 300 meters, the larger aperture works out to about a 200-meter zero. This gives a usable battlesight zero (BZO) from 0 to 200 meters, hence 0-2.
In addition to this article, you might want to take a look at my Complete Guide to Your Iron Sight Zero. In that article, I go into depth with how the angles and calculations work for iron sights. It provides a lot of context to this
The large aperture works great for fast-paced run and gun where tight accuracy standards are not required. However, it’s not ideal for marksmanship practice where precision is the priority, it’s just to large.
The best accuracy comes from allowing you to use the small aperture at a closer range than 300. Let’s make that adjustment.
Revised Improved Battlesight Zero (RIBZ)
In 2010 when I first got into ARs, I read a thread on M4carbine.net about Lt. Col. Chuck
The takeaway was that a 50-meter zero was a good all-around setting for backup iron sights on the AR-15 platform. Kyle Lamb said the same in his excellent book, Green Eyes Black Rifles, which I purchased while planning my first build.
I did not have a carry handle sight to worry about at the time. I was sure I was always going to use flip up sights paired with optics. Because of that, I never paid attention to the carry handle IBZ procedure. I simply set my backup sights to 50 meters and forgot about them.
Until my frustration at the Appleseed event.
The RIBZ sight setting takes the Santose IBZ one step further to achieve a 100-meter setting. The beauty of it is that you can still take advantage of a 50-meter setting as well.
All it takes is adjusting the rear sight drum.
Adjusting the Drum
To implement the RIBZ sight setting, you need to allow the elevation drum six more clicks below the 6/3 setting.
For an 8/3 rear sight, found on the A2 drum, you only need three clicks. The A2 drum has one minute of angle (MOA) adjustments, while the 6/3 has half MOA.
Molon recommends adding one extra MOA of buffer space to prevent the rear sight housing from making contact with the frame. That means one additional click on 8/3 sights and two extra clicks on 6/3 sights. This allows you to get a more repeatable zero.
Locate the Set Screw
Set the sight to the bottom setting, which should be 6/3 for detachable sights. Looking down from above, you’ll find a witness hole with a screw at the bottom.
To slip the drum, insert a 1/16 Allen key and loosen the screw.
Do Not remove it.
Loosen it enough that you can rotate the knurled bottom part of the drum. Done correctly, you can rotate this piece individually from the numbered portion.
While keeping the Allen key and the top half of the drum in place, rotate the bottom half clockwise for eight clicks. If using the A2 8/3 drum, only go four clicks. Once the drum is slipped, retighten the set screw.
You can now turn the rear drum eight clicks below the official bottom setting of the 6/3 sight.
Turning two clicks back up, so it’s 6/3 minus six, is the new 100-meter setting. Two more clicks up, 6/3 minus four, is 50 meters. The 25-meter zero remains at the 6/3 marking.
Now you have settings for 100 and 50/200 meters. The markings on the drum for 300, 400, 500, and 600 meters remain accurate.
The Front Sight
This procedure does require resetting the front sight post to the correct height. Since the entire rear sight assembly has been raised by several MOA, the front needs to be matched.
Note: The above description of zeroing at 25 meters using the 6/3 sight assumes a carbine length sight radius and barrel. If using the RIBZ on a full-size rifle, as I do, then click two notches up to the “Z” setting for your 25- meter zero, and then continue using the 300, 50/200, and 100-meter settings as normal.
I hope you found this useful. I came across several rifles in military armories that had this process performed on them. Frankly, I think it should be part of the technical manuals.
After completing RIBZ, you can keep your elevation drum accurate and use it for 50, 100, 200(ish), 300, 400, 500, and 600 meters. Good luck!