Bear in mind in LW I work using real world scale.
I prefer to use "1m = 2^1.42 bananas" myself, but maybe it's just me... SERIOUSLY speaking, gun looks good to me, bit low-poly maybe (wait till you see my gun...) but good nevertheless and suitable for low-HW games too.
I wouldn't worry about reducing "not-seen" polygons from the hand - modern hardware (GF1 and up) does not really care if it's rendering 500 or 1000 polygons; the speed is same.
If someone wants to use the hand for pressing a key from a keyboard in the game then it would be handy (pun intended) to have all the polygons on the backhand too? :)