I wouldn't have guessed that .38 super is hotter than .357. I learn something new here every day.
How do the velocities compare?
If .38super is a shorter case, so I assume it uses a faster burning powder, and doesn't maintain peak pressure as long (though I could be wrong). If that's the case .357 seems like it might wind up being faster - at least out of a longer barrel.
Either way I'd like to more about it.
I have to confess I know basically nothing about .38 super.
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