J.M. Browning, the icon of all gunmakers, died in 1926, long before the need for anything bigger then .50 was felt within USAAC and/or USN.
We've had the similar discussion before, mentioning the Russians, Germans and Japanese successful ,results in up-necking. So the same could've been done in the US (and it would've been a good thing), providing a request by the USAAC/USN, even without J.M.B. around.