Daryl, most double rifles that are chambered for a rimless cartridge use a small spring loaded extractor blade within the main extractor leg. The difference here is the very large surface area of the extractor blade and the fact that it is mechanically raised after the cartridge is in the chamber when the action is closed. Then when opened and extracting the the taper on the case head behind the rim easily moves the extractor blade downwards to allow the case to fly out unhindered, with no resistance of trying to push against a spring.

Matt.