Here is the latest round-up from Michael Goldfarb, who has done wonderful work on this story. The latest question being raised, per the American Spectator, has to do with an earlier Scott Thomas story and square-backed 9mm shell casings.
UPDATE:
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The firing pin in a Glock is rectangular in cross-section, and leaves a “squarish” imprint on the primer when firing a round. The cases are round, as are all current standard ammo.