Suicide Orc

I apologize in advance if someone has asked this before, but when the Orcs stuff the powder in the wall and the Orc sacrifices himself, was the powder gunpowder? That is what I thought it was. And then I thought, if they can have gunpowder to create explosions, then how come Sauron didn't just create a gun to blow Aragorn or somebody away right then and there?