Reading the PDF, well, its a neat idea, but I don't see how a rifle using Gunslinger can possibly keep up damage wise. Technically speaking, they can't use vital strike, and they can't use iterative attacks. Like crossbows, many of the ranged feats don't apply. Oh, and 10 gp a shot? Ouch. That especially hurts for the pistol packer, who are otherwise better off, but still can't use some of the best ranged feats. The actually having iteritives helps, especially with them being ranged touch attacks. But your going to be going through mounds of gold if you are going to be shooting off like an archer.
I like the grit mechanic, mostly, though the cauterizing barrel trick seemed awful silly to me.
Also, skill points. A few more would help.
If I seem all down, it is because I WANT to like this, I WANT guns in my fantasy.