MGC P220 + Marushin M39 feeding issues

Hi all !

I always had feeding issues with my MGC P220 and my Marushin M39.
Especially with the M39.
I have notice that the magazine is a little bit loose (only on the Marushin M39).
Is it normal ?
What part should I check ?

According to this page :

http://toku.ninja-x.jp/english%20model%20auto%20page10.htm

the magazine seems to fit well but not on mine.

Otherwise I have not this problem with my Tanaka Glock 17 or MGC Beretta M9.
I can cycle and empty a magzine without any problems.