A camouflage pattern would not help, no - it would just make the shapes you do have read worse. You just need to adjust your existing colours to have better contrast, and possibly more interesting hues, that's all - to fix the colours, anyway. There is some pixel work you might want to do to fix the banding.
The drum magazine looks much better! Now make the rest of it look as good ;D
Tried to make a drum magazine, like you suggested.
For the lack of colors/contrast would a camoflage pattern help?
You had the same problem with the other piece, it looks very flat as it is.
Place the shadows smarter (and in some places bigger) to convey the form better but most of all, add some contrast.
The banding on the stock and grip makes it look blockier than it's probably meant to. Ironically, the banding is also the only way that the shading stands out - everywhere else, its low contrast and nondescript shape just makes it look like your lineline's blurred. All of your colours are very similar, to the point where perhaps using solid colours with no shading might read better. If you're going to have those extra colours, put them to work! Make them different enough to make a difference zoomed out.
I realize the AA-12 has a very boring shape, being basically a flat block, but your art of it doesn't have to be as boring. Why not make the magazine be a drum, so it can have more interesting shading? Why not put a grip on the barrel so that you can have a more interesting silhouette and again, more interesting shading? You can make this painfully boring gun be quite interesting with just some minor modifications, and that's not even going into accessory/attachment territory, which may also be an option for you!
Not forget this piece, I am still working o it and tried to fix it with the existing palette.
Hope that this one is better and not to much patterned.