Smash,
I posted up a thread about Ordinance info a while back. It's just stuff I found off other IL-2 forums, so it might help...
http://www.dangerdogz.com/forums/index.php/topic,2956.msg24365.html#msg24365
AB bombs are cluster bombs. Try it on trucks or other soft-skinned vehicles instead and see. Although in that thread it says they're armour-piercing.
Also, I don't think dive-bombing would be the best way to deploy these bombs, ideally flying straight and level would disperse them over a greater area.
p.s. I'm not sure if you'll be able to see this post I linked, as you don't appear to be a fully fledged DangerDog right now.