[KraMax]

To descriptions to BMP-1 and BMP-2 - it is written that them armour can to protect them about splinters of shells, bullets and small-caliber shells autocannons. I think that it fairly for front and side armour - though is not assured.
In description BMP-3 - it is written that it armour maintains any shots from machine guns on a circle - front, side and rear. And front armour maintains sabot shells 30mm from penetration from distance of 300 metres.