I have observed that the cartridge retainer finger section of the extractor should be completely clear of the breech block end cartridge counter bore when the cartridge is released. At that point there should be additional clearance before the extractor engages the small inner flanges of the breech block.
However, if the clearance of the extractor to breech block is insufficient or the ejector is too long, either situation might be forcing the extractor vertically into the inner breech block restraint flanges.
I suppose that if the loads are too hot the increased recoil could contribute to this damage. You did state that the cartridges were standard Federal 9mm Luger ammo. Is that a hot load?
We have more in common than Lugers, I served my Apprenticeship as a Tool Maker before going back to college to become a Mechanical Engineer.
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