Summary
This is a remix! I like the design and made some changes. The mount can use more work.
You can Sew up a bag from old blue jeans with a zipper to catch the brass, or just use it as a brass deflector. Make shorter or longer as needed for Mlok or Pic rails.
Enjoy!
Remix Folding Brass Catcher 224 Valkyrie 3D Print Model
