Quite nice 0-L-A-F, the buy image is quite well done, if a little bit chunky, and is definitely what many know as the M4A1.
Only problem: The drop image is huge!
Additionally, I noticed that you used alpha while creating the buy image - And as such you didn't make sure that all of the weapon was a grey colour - I see pinkish greys in the colour that the background is.
Might want to fix that~