[Dixielandjazz] What's a "32-20"? (was More Jazz Musicians who carried Guns.)

[Robert Smith]

Robert Johnson sings about a "32-20". I have a plea to all you gun experts: 
What's a 32-20?

Incidently, my impression is that everybody in the US of A owns a gun, and 
will use it on the slightest provocation. This impression is gained from all 
the American TV programmes that are sent on Norwegian TV. It may well be a 
distortion of the truth.

Cheers

Bob Smith