The gun is still here. I have decided to have a set of new barrels made up i a .500 straight case. I have here recently found one here in Denmark who had some 350 pieces of .470brass. That can easely be mase into .500 3Ľ" cases.
The .577/500 magnum is apealling but a pain to find high quality brass for. With a new set of barrels I can shoot fra lead to steeljacket bullet without fuzz.
Then chamberwalls will become thicker but it can take a slight higher pressure. To drive a 440-500 grain @ 1900 ft/sec should be well reached. Maybe a leadbullet of 570-600grain @ 1700 ft/sec would knock a buff over.
I love this HH gun. Far more interesting than any modern dr. I wished they still made such actions.