basically the mag ran back from the front of the gun into the spokes of a wound feeding mechanism, and while it was under tension (along with the caseless ammo helping in this regard) it would feed the rounds into the chamber, there was more than likely a sort of ratcheting system on the winding feeder that would stop the feed after 3 rounds (though it could disengage to allow for full auto at a much lower rpm). though the exact specifics of rounds being fed (whether by ramp or other means) and the mechanism causing the magazine to reciprocate (if you see the gun fired, the magazine moves back into the gun, more than likely to manifest the placing of rounds into the tension feeder), I have no idea, and this is all speculation that I can gather from a simple-minded engineering standpoint, and we all know that it's not the same as a German engineering standpoint. hope I helped though, if you need more information there are a handful of youtube videos I've seen of it being fired and what the tension feeding mechanism looks like, though it does not have a complete breakdown or explanation of operation