I have found that the Cyma CM040d does not take all brands of mags and other reports on the internet that the other brands were not working, I found some reports of people that have replaced there hopup units with Cyma metal hopup unit and having a problem to get there existing mags to fit.
So after looking at the stock mag of the cm040d and then the other brands, I saw that the only differences is that the small ball(bb) catch in the mag well has a bit taken away in the middle, About the size of a 3mm drill bit, where as the other mags is not and flat. All you do is file or demrel out a slot/ groove / channel in the middle of the top part of the ball catch, about the same as the cm040's mag, Just be careful not to grind out to much or when you wind up the mag , the bbs will top out of the feeding hole/ well .
After doing this mode to all my mags work fine on the CM040d and my Kalash's, even the AK47 type mags work after this mode. I did fine one mag that worked with out modes was the JG short hi cap 250rd , fitted prefectly.
I will try to do a some pictures and post them later. BEWARE DO THIS MODE AT OWN RISK :hihi:

myself, have found that one of three things can lead to AEG mag incompatibility and/or malfunctions:

1) mag catch at the back of the mag

2) bb stopper in the bb feed channel of the mag

3) mag catch lip at the front of the mag


waiting for your pics and guide, komrad

a is cm040d mag
b is stock mag ak47 no name brand and what most other mags have .
c is a Kalash RK02 mag with mod
d is cm 036 mag mode
e is the JG short high cap which was the the only aftermarket to fit the CM040d

After doing this mode all mags fitted find and worked. They even work on the same aegs that they came with
Will post pictures of the different mags on cm040d later.