I'd up the damage dice on the one-shot weapons to make them more useful compared to a bow and arrow. There's a gun thread right above this one where I lay out my firearm rules with a few explanations. I also lay out rules for suppressive fire and a few feats. Note that I designed my guns to fit into D&D, not mimic real-world firearms.
For instance, looking at the pistol, is there any advantage to carrying one over a bow?