Just wanted to report that the Gunslinger feat works for the chemical and energy pistols on my game.
Actually, only the 3AP reduction works. The +7 initiative doesn't.
But I really liked this "bug" on my last playthrough, with my chemical/energy pistol guy focusing on critical damage.
With 10 dexterity, I was able to shoot 3 times per turn (without point shot) : 3x laser pistol or 1x chemical pistol + 2x laser pistol.
And was able to have 6 strength (steadfast aim), 7 agility (interloper), 7 intelligence (mad chemist, practical physicist), 10 perception (sharpshooter) at level 25.