jimmyj - Barnes cartrige book says the 38 Special and 357 has a rim diameter of .440" and 38S&W has a rim that is .433". The case of a 38 S&W is .007" larger than 38 Special.

I have trimmed down lots of 38 Special cases to load 38 S&W. The first time they are fired, the case expands to fill the chamber and subsequent loadings seem to load and shoot very well. Actually, if you use the larger bullet (.360"), the case will expand as you load that bullet the first time to almost the 38 S&W neck diameter. I have factory 38 S&W cases as well and do not see any accuracy difference between the 2 case types.