This is a remixed design of a Nerf Rival Magazine Holster.
The original author did not provide a step file, so I created my model from scratch in fusion 360
...Show more (basing some geometry on their design).
I modified the cutout geometry so that the holster would easily accommodate both 7-round and 12-round magazines (which have slightly different profiles).
I only printed with 10% gyroid infill. It seems plenty rigid and sturdy, but we'll see how long it holds up after extended use. Feel free to print with a higher infill if you desire a more robust product.
I've uploaded the Step file I created to make it easier for others to Remix (as needed).