O)K, thanks, I knew there was a difference, ,getting old! lol
With the 357 it is the case length, I spoke with a S&W factory rep about how the 38 model 10 seemed the same as the following series revolvers in 357, he related it was the cylinder length that was increased to allow 357, otherwise they were equal.
I think there is a difference in 223 and 5.56. as well, and yes there is a difference in the pressure.
best wishes