Vic,
Parent cases are no problem, 9.3x74R cases are easy to get.I'm sure there is a standard width/depth for extractor grooves, but the easiest way to do it would be to grind a tool to match the groove in a sample case( 8mm,30-06,etc).It's not very critical anyway.Be sure to slug the bore before ordering special bullets, a lot of 9mm rifles take standard .358"bullets.
Mike