I didn't thought I would add another post to this thread but here I am I guess.
So yeah... I wasn't fully satisfied with how the weathering turned out so I did a black wash. Why didn't I do it earlier you may ask? Here's the answer.
Previously when I was working on my cosplay I fucked up while doing the black wash and had to repaint one of the parts. And that was the day before a convention. I was really mad at myself but I pulled it off. And when I was making my MA40 I was a bit anxious and skipped this process. But as it turns out without it the prop didn't looked quite right for me. So I tried my best at black washing once again. And here's the result:
It may not be perfect and I'm not 100% happy with it but it's better than it was before. At the very least I won't regret that I didn't do it.