There is a French fellow near Grenoble who makes a modern day version of the Heeren. I had a link once but not now - I remember getting it from some single shot forum - a poster listed current manufacturers of falling block single shots. Sorry I could not be more informative.

years ago I tried out a matched pair of cased Heerens, gorgeous rifles, by Glaser of Zurich, in .30'06 and .220 Swift.  Had to kick the levers to get them to extract.

Thank you much for that link to another maker of Heerens. I wonder if these companies make their own actions or if there is a single source in Europe for the unfinished actions.

There is no question the Heeren will be weaker in extraction. Look at the action's drawing, in de Haas, and you'll see there is no leverage given by the fingerlever onto the extractor.  Extraction force must be about 1/3 that of the Hi Wall.  Of course, weak extraction means rapid extraction, and the simple extractor will likely function as an ejector -- if the case doesn't stick.

I have to believe that if the pressures are low and the barrel is suitably thick, the case will never bind.  The best explantion for case stick I've seen is that the barrel expands on firing, the case deforms, and then the barrel springs back more than the deformed case. Lower pressure means less deformation in the case, and thick walls mean less spring back of the barrel.  I don't know what works in practice, though.  Apparently '06 pressures and diameters don't work in these.

The Heeren's compactness comes from placing the trigger face nearly directly under the breech face.  I wonder how ergonomic that would be.   

I'd really like to fire one of these in .30-40, or 9x57R, etc.