Cool to do new weapon :) I had the same weapon animation idead but with a flying ball (lol), but i'm not good with bones animation i have to read some tutorials :D
But I think You can Do better, i explain:
-the skin: the left face is good, but the top face is bad, textures are ugly, you didn't do a good UV skin, I think that's it. And i don't like the green part :s search some tutorials to do better UV skins and will be good weapon.
-if you don't find, move you model to left/top for we can't seethe top of teh model, or maybe try to rotate a little... you have to try some technics, but i think creat new uv skin skin is better :D
ps: 3/5 for the moment, I'll change if you modify what i said ;) enjoy