"I wonder how a .22 can run the action"
Well, it doesn't run the Parabellum pistol action. The Parabellum pistol is a locked breech, recoil operated pistol; the Stoeger Luger is a straight blowback. The toggle on the latter is not locked and imposes minimal resistance to the blowback action. The same is true of the Erma gun.
It is worth noting that in the 1920's, Stoeger was the authorized importer for the Parabellum pistol; they trademarked the name "Luger" in the U.S., which is why the pistol is called that here even though the rest of the world calls it the Parabellum. Since Stoeger owns the name "Luger", they can sell a pistol and put the name "Luger" on it, but Erma could not put that name on their gun, which actually looks more like the original.
Jim