The SM pilots targeted the wing fuel tanks - a few phosphorus type cannon shells in the Engines/Fuel Tanks would have been enough to bring the Bomber down.
The ammo used was a mixture done by the waffenmeister according to the wishes of the pilot.
normally 1 piece of explosive- Minengeschoss, then 1 phospor-fire - Phosphorbrand, and 1 tracer ammo-Glimmspur, the last not too bright.
Minengeschoss = HE
Phosphorbrand = Incendiary
Glimmspur = Dim Tracer