I recently bought a GSG-16 and it's a very fun little plinking rifle. Unfortunately it's proving pretty painful to break down - so I wanted to stick it in a rotating vise for easy access/positioning.
I was disappointed to discover that the GSG-16 isn't common enough for anyone to sell locking magwell vise blocks. The upside of this was an excuse to get cozy with SolveSpace, a very cool parametric CAD program I've been wanting to learn. And it's FOSS
The image above is an auto-generated (!) view from SolveSpace. Below you'll find a few pictures of the final product, and finally the stl. I guess it shouldn't be surprising that a parametric CAD program can draw detailed technical drawings on the fly, but I still think it's cool.
File download here