Back in post #4 reference is made to John Browning. Browning did not design the M12 Win. I believe that the designer was named Johnson.
One problem with the pre WWII 16 ga M12 is that it is not easily converted to 2 3/4" shells. The earlier 20 gauges can be converted by just reaming the chamber longer, but the 16 also requires that the ejection port be lengthened to get reliable ejection.

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Tom
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