Expanded Sunder (3.5e Variant Rule)
From D&D Wiki
Expanded rules for Sunder Attack option
About the action of sundering projectile weapons, I find that the core rules are lacking a slight correction. For instance, I disagree with the two-handed weapon classification for longbows and shortbows. If we look at the weight of longbows and shortbows (3lb and 2lb respectively), we see that they are, in effect, LIGHT weapons. And although a warrior requires both hands to use it, they are not as sturdy as the pole of a polearm or greataxe. Furthermore, as for hardness and hps, the only reference made in PHB is the "crossbow" (PHB p.158) with 5 hardness (wood) and 5 hps. There is also no distinction between heavy or light crossbow; which seems another incorrection.
My interpretation and suggestion is to consider: 1- all projectile weapons one handed melee weapons (except hand crossbows, which are LIGHT weapons), 2- composite weapons should have hardness 7 instead of 5, same as Tundrabows (because they're made of several different materials bound together with a high strength rating); 3- Heavy crossbows, Greatbows and Tundrabows should have 10 hps; longbows 7 hps; shortbows and light crossbows 5 hps; hand crossbows 2 hps.
Note: this is not a change in the rules, but simply an improvement to an attack option which is lacking a few minor additions/corrections in the core rulebooks. You can use it as core 3.5 rules without fear of unballance.
Note: I'll try to add other projectile weapons such as Arbalest when I have the time. Enjoy!