I noticed some AK style weapons (AK47, AK74, SA58, PKM) have their minimum zeroing set at around 440m, but when attempting to zero DOWN, it does nothing. However, when attempting to zero UP, it goes to 100m, 200m etc.
I don't know if it's a feature or not, but if it is, it it inconsistent with the other weapons that do not have it.
It may be a coincidence, but it does not seem to affect weapons that do have a "hundred only" steps, only those with default as 440m, 420m etc.