Ok, time to wrap it up, and I would like to thank Sheepherder for the moral and technical support he provided for this part.
The ramp cut was pretty straightforward, I set up the barrel for a cut 50 degrees off the centerline and cut it with a 10mm end mill. It's fresh out of the mill in the picture, so it still needs a little blending to break the sharp edges.
One thing that puzzles me is the width of the original ramp. The drawing shows a straight ramp with a 5mm radius, but making that cut with a straight 10mm end mill creates a ramp that's more like an ellipse where it intersects the end. After eyeballing and gauging several original barrels I realized that these cuts are not cylindrical. They actually taper a bit, thus creating a wider throat at the bottom. I have seen similar ramps on barrels made for rapid fire with double stack mags (the M4 ramp comes to mind), but I can't see that it would be of any benefit on a single stack semi-auto.
I guess the original shape is just a result of anal German engineers trying to follow a drawing that wasn't fully thought out, and a straight, cylindrical cut should actually work better IMO.
The extractor cut was a bit more challenging due to its shape. You can cut this with straight cutters and then use needle files to round it off, but after a few hours on the internet I found a corner rounding end mill that could do the job without any hand adjustment. The dimensions are slightly different than on the original drawing, but the objective is a nice cut with ample clearance for the extractor so the actual dimensions are not extremely critical. I checked for clearance by holding a breech block against the finished cut, and it fit nicely.
This concludes my part of the project, so the barrel is boxed up and will be heading for AZ today. Just some finishing work and installation left to do, then it's ready for the range.
