I find the weapons that tear up vehicles in canon seem less than effective in the 40k rpgs. So two possible solutions, some nicked from elsewhere (would credit if I could remember sources):
* Weapons traditionally designed for tearing or piercing vehicle armour gain x3 Pen versus vehicles. These include melta bombs, krak grenades, power fists, krak missles, lascannons, melta weapons of all sorts.
* PCs can choose to target weak spots on vehicles (e.g. hatches, viewports, gaps between hull and tracks) at penalty (-20 upwards depending on target) but get to halve vehicle armour for that attack if successful.
Any thoughts?