The .357 magnum is a +P cartridge to begin with and they should not be marked either way. It is true that some loads are loaded lighter than others, however.
You do get better than .38 special performance out of a short barrel revolver. If shot from a shorter barrel, the performance of both .38 Special and .357 magnum is reduced. However, some loads of any handgun cartridge will perform better than others from a short barrel. That's not saying they perform better in short barrels than in longer barrels, though. Blast and recoil come with the territory but lighter bullets have less kick. Muzzle flash is not the same thing.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
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