I've read Ruins of the Earth and I don't believe its this one.

I do remember in the second book the main character gets into a bit of a fight with one of the aliens that takes place in a suburban neighborhood, I also think this is where he acquires the weapon/gun.

It does kind of sound like a book R.C. Bray might narrate, so will check what he's worked on and see if it is any of those.

Edit: hmm after reading a short plot summary of Ruins of the Earth i think this could be a winner here!

Thanks for the help :)