Pros:

-Looks great!
-Weapon from CoD!
-Makes killing zombies more badass
-Don't feel like changing weapons even when there is no ammo!

Cons:

-You should change the "clip_size" to "6" in your weapon script to make it fit the model perfectly.
-The stock is blocking the right side of the screen(I don't mind it,though)

Conclusion:

Fantastic! I was searching for this ever since i played with mods! It just needs a little bit of tweaking and its perfect!