Great find! 9mm ammo is relatively inexpensive that means more shooting

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All the Six models, that I know of, were built on the 357 frame.
The max SAAMI pressure for the 357 =
35,000 psi
The max SAAMI pressure for the 9mm+p =
38,500 psi
SAAMI pressure specs
Be careful! The 9mm+p is not the same as the 38+p. The smaller case can be decieving.
To bring a 9mm to higher velocity a faster burning powder is needed due to case capacity, this in turn creates a higher pressure. A 357 can create a higher velocity at a lower pressures, because of it's larger case. The slower burning powders distribute the pressure throughout the chamber and barrel rather than in one tight spot. Having more case volume allows you to use more "slower" burning powder. That is why you see so much fire from magnum loads in a 357 snub (powder still burning).