Currently, there is NO IC² addon that is intended to work only for weapons.
Really, I wish i could use all modern weapons, like automated guns and nuclear/biological/chemical warfare, causing devastation to everything!
The only problem about Minecraft is the lack of armies, aka enough players to create a real war.
There could be an addon that allowed us to create entire armies of soldiers, spies, pilots, whatever people is needed in a war, everything controlled by AI, following your orders.
For example, A multiblock machine that allows the training and creation of soldiers, armed with weapons you create through military industries.
AI combats, different behavior with different weapons, different targets, better/lower effectiveness due terrain (biome)...
Anyway, thats just an idea which would fit the industrial concept, but it needs an insane amount of work to make it reality (code-wise).