Ruger just did exactly that with their LC carbine. Went from 5.7 to 45 acp. Granted this is not an apples to apples comparison as 5.7 is longer than 9mm or .40, but it produces much. Less recoil energy than either. It may be more hassle than making it in .40, but it is certainly doable. Add that to the fact that there are a lot of us that prefer our calibers to start with a 4 and they got reason to make it.

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Please no more EZs...