>If the ejection port is open on both sides, what determines which way
>the casing is ejected?

There's always some inherent variation, but the extractor and ejector in any given autoloading firearm will cause the spent casings to trend in a certain direction based on their geometry. In almost all designs where the cases aren't ejected from the top, they go out the right side, because that's the side that's more convenient for the majority of (i.e., right-handed) shooters. That's still the case in firearms with a one-sided ejection port; they don't just rely on the position of the port. That would lead to a lot of failures to eject, as cases left to their own devices went anywhere but out the hole. :)

--G.
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Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Mod
Eyrie Productions, Unlimited http://www.eyrie-productions.com/
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