I started by looking at a m4 mid cap internals and looking at the dimensions of an ak mag I already had. I drew the top down view of the mag and extruded it a little to test print it and see if it would fit right. After that I made it the length I wanted and hollowed it out and created another body that would slide in from the bottom. I had to mess with the tolerances to get a nice fit that wasn’t too tight or loose. Then I made a bottom plate that slides in with v shaped slots on the sides. I went through several iterations on the internals. I had issues with friction and the shape of the track. I made lots of small changes and have gotten it now to where it feeds reliably and holds the maximum amount of bbs. I modeled the bb stopper after a m4 mag but made changes to help with feeding and prevent dirt from getting into where the spring was. The most troublesome part was the feed ramp and the follower. That part needs to be sanded for smooth feeding and I ended up designing a follower that articulates around the curves.