You can learn more about the 38 Super round by visiting here...
This site contains and links to, information on loads both handloads and commercial for the Super. As well as other useful information.
The Super is not as powerful as the .357 Magnum due to it's lesser case capacity and case design (the Super is the old 38 acp round just loaded more powerfully). But does come very close to what the .357 Magnum can do in defensive loads.
The .357 Sig round is a bit faster with 125 gr. bullets but loses some ground to the Super with heavier pills.
A wheelgun in Super is an intriguing idea.