Recompiling Bombgun and Bomb classes were always a problem - The only solution, and a painful one, was Jabaytes till Loku posted the following sometimes ago - and it works:
"I had same problem when tried to make new bomb,cloned classes with new names dont work even when compiled correctly,game loaded without crash plane appear in qmb window but only option for weapons was Default,than i asked my friend who is skilled with java and he told me its a decompilation problem,to make it work i need add (Object),its a example from BombGun class wich caused problem:
Property.set(class1,"bulletClass", com.maddox.il2.objects.weapons.BombPuW100.class);
add (Object)
Property.set(class1,"bulletClass", (Object)com.maddox.il2.objects.weapons.BombPuW100.class);
now its working without any problem.Maybe it helps you ,and it may solve some other problem with some classed we had before on other mods."
I tested it and ....it's one of the things that convinced me that Eclipse is the best option for writing and compiling classes for Il2