The majority of the parts have proportion errors, look at the front sight, charging handle and the receiver cover. If you compare your AKS to a real one the mistakes become quite obvious.
+16 tris takes literally no performance. Or if you really think its a waste, why don't you just ignore the error if it will be actually mostly covered up by other parts.
Hmm strange, your bake mesh maps all turns out black. Anything else you changed other then the match by name setting? Is there any error on the log window?
Post your model, or a simplified version that causes the same error. And your step by step workflow. You're probably doing one thing in particular that's causing so much trouble.
Okay, I'm back on it. Reworking the body and fixing any previous errors so I can get her ready to be rigged. Clothes will be redone with Marvelous so missing for now.
@llRobinll Thank you for feedback ! :D @Pixelgorilla Thank you for comment ! When I pose I'll do asymmetry and I will fix these errors in hand. I started the textures.
Textures are looking good. In your breakdown shot turnaround you may want to tone down the backdrop on the object as it looks like a weird error at first glance. Otherwise awesome!!
Sorry no crits other than what's been mentioned about the baking errors, apart from that... looks awesome, love Akira and you've done a great job so far!