It's nice, but I really want valve to stop it with the bullshit half-cosmetics that are never worth anything, so I think you should add something cool and noticable to it. Like more belt stuff or a tube at the bottom that connects to something else. Otherwise, I think it's pretty good.

particle affect green smoke?

Zyklon-B!

I'm with darude&storm- your texturing is solid, but perhaps you could collaborate with geometry artists on Facepunch and the like? It would certainly give you more experience, plus allow you to work with higher-quality weapons models.

did you texture this?

Damn straight

Just wondering, don't take this as an insult: you've collaborated with Rozzy, you regularly upload to the workshop, and you seem to have a grasp of the game's color scheme. But why don't you try to improve your modeling skills by communicating with people through TF2 modeling sites (Facepunch, Polycount, etc.)? You're fairly close to making items that are of good enough quality to get into the game, but your model geometry is holding you back.