Designed this in tinkercad to hang an AR15 on the wall. It could probably be better, but its strong and holds the firearm solidly.
I ended up mounting one to the side of my workbench as well for holding the rifle while working on things that don't require a crazy amount of torque.
It would be cool if the mount looked like a PMAG, if someone better at modeling then me wants to remix it.
Only use supports if your printer can't print the screw holes.
Mount it to something. I used random wood screws into a stud.
Took a lower vice block and made a bunch of guesses. It worked.