Hello, everyone,

While rummaging through my hard disk I found this file very well designed: a RIS type handguard for MP5K.
You can found the source here https://grabcad.com/library/stinger-r36-airsoft-gun , to go and thank the guy who designed everything

[Edit 13/12/2018]
I finally found on a used mp5k JING GONG and printed the part on HP MJF. (Fixing part : RightHalf because one of hole was not open)

The assembly of the parts is done with M3x15 screws and M3 nut,

It is almost perfect assembly on the replica EXCEPT at the front of the magazine where you can see that it forces a little (see pictures), maybe the replica dimensions must be slightly wider than the part so be careful when you tighten everything.
So on a replica Jing Gong it goes by forcing a little, to see on the other models....

Good printing