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Improved Battle-sight Zero

Improved Battle-sight Zero

IBZ stands for Improved Battle-sight Zero. The common drum elevation adjustable rear sight can be tuned to achieve some great versatility. The method for adjusting  for A2 and A3 drums is a simple process. Before we begin remember that a detachable carry handle on a 20 inch barrel translates to a 1/2 MOA adjustment for windage and elevation. This makes a flat top 20 inch rifle with a rear drum a *very* precise machine. Contrast that to a fixed carry handle which adjusts against 1 MOA clicks for both windage and elevation. This doesn’t mean that A2 drums aren’t precise… but if you are going to give high power shooting or XTC a try with your fighting rifle *as is* then you would do best to take an A4 with detachable carry handle.

What the IBZ does is allow for adjustments to be made below the 6/3 setting of the elevation drum. Instead of using the large aperture for 0-200 meters, you can configure your rear sight with the IBZ method and get a working 50 meter zero using the small aperture and yet retain the adjustments of 300-600 meters. The 50 meter zero is amazingly useful. At the apex of a 62 grain bullet’s flight path with a 50 meter zero you will see about 2 inches of bullet rise. The projectile will cross your line of sight again at 215-225 meters roughly. It will then drop from 4-6 inches right before it crosses the 300 meter mark.

Simply re-adjusting to the 300 meter mark on the drum will alleviate that problem quickly.

Here is a quick tutorial for the IBZ:

Click on the first image to start the slideshow.

 

DPMS rear BUIS IBZ

DPMS rear BUIS IBZ

DPMS rear BUIS IBZ

DPMS rear BUIS IBZ

DPMS rear BUIS IBZ

To adjust a A2 upper for the IBZ set to – 2 clicks instead of the -4 clicks above.

While the Revized IBZ is also popular at the moment I find that the IBZ is simple enough and that tuning the drum even more to get a 50 and 100 yard zero seems unnecessary. For targets at 100 meters I simply use  a 6 o’clock hold with a -4 click setting. Furthermore adjusting a carry handle (or A2 drum) past -4 clicks can put us into potential error territory. If I want a 50 meter zero I simply use IBZ and bottom out my drum. It wont go past -4 clicks so I can’t go past or screw up my very useful 50 meter zero. If I were to use RIBZ i could adjust to -6 clicks below my 6/3 mark on my detachable carry handle. All that just for a 100 meter zero. No thanks!

The IBZ is simple, relevant, and the 50 meter zero is a great zero for the 5.56 cartridge. I hope you don’t need much more convincing if you haven’t done this already. 🙂

Written by lothaen

1 Comment

  1. Martin Sprick · October 31, 2017

    A2 windage is 1/2 MOA, not full MOA.

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