NotaGuntuber on the sea has a video of him making a bronze one. He involved some CNC work, but it can be done by hand. The tricky part with the bronze is getting it bored out to .75" as the tubing comes smaller. Patience and lots of stepping up of bit sizes followed by a .75" reamer will get you there.

I’ve been wanting a Ruger MK for a while. Plan on building as many as I can. 😁

I have one in the plans for the future along with a bronze body, but both I’ll probably be doing those as a MKIV once I convert the jigs (assuming its feasible). Those are plans for after I finish my MKR(evival).

They used the Hitchhiker retractable stock.

Also, you’ll need the FCG reinforcement plates. I couldn’t find any STLs for them as these being 22lr, we don’t need titanium or stainless, so printed ones are fine. I had to convert the DXG files to a sketch in Solidworks and create the STL from that.