Good news! Got my Cyma metal AK mag and tried it, didn't fit.... so I began filing the part in the green box bit by bit and trying it. Eventually I filled enough off for it to fit snugly It feeds fine until there's about 10 bbs left in the mag and then gets temperamental but I think that's the mag more that the gun. Here's a comparison: As you can see all I had to do was file down the bit above the lip including the top edge. Looking down the magwell this bit in red was the culprit: One question though, is it normal for mags to misfeed when there's a few BBs left? I'm thinking it's due to the fact it's a CYMA brand, I might get a 72 round TM mag and give that a try.