Anyone know how to do this?

Thanks for any replies.

Just sight in using the big aperture at 50yds.

The ARMS #40 isn't elevation adjustable so the second aperture is kind of impractical using the IBZ. The small aperture has something like a 375yd-400yd zero with the big one set up for IBZ which means you are way high at closer ranges(around 6" at 100yds).

Other alternatives are:

1) Foregt IBZ and sight in at 25/300 per military style.
2) Replace with a same plane aperture. Now both apertures can be used with the same IBZ.

IBZ uses the small aperture.  Same procedure applies with these sights -- or the M16A1 -- you just don't get to click up to 300 meters and beyond.  No targets out there anyway, so there's no need to shoot at them.  That's why this is called battlesight.

-- Chuck