It needs some sanding on the bottom after printing so it fits more smoothly.
To get it off, you need to poke a small screwdriver, stick, cleaning rod, etc. down the hole on top and push the baseplate off.
Enable support everywhere.
If the thin walls don't stick to the bed or cave in a bit, just add a brim in your slicer software. About 5mm should be enough.
If the inner part of your magazine is a bit loose after installation, put a piece of tape, between the baseplate and the magazine. (should not be necessary tho)
GLHF ^^
The author remixed this model.
Made to fit the Krytac M4 Airsoft Magazine