There is several thousandths difference in diameter between .38 S&W and .38 S&W Special cases.

Yes, you can make .38 S&W ammo from cutdown .38 Special or .357 Magnum cases, but you will get that characteristic case bulge from firing in a .38 S&W chamber. Not enough to worry about, usually, if you are loading to starting load pressures.

Please be advised that the only gun I have ever damaged was a late 19th century black powder breaktop .38 S&W. The starting load of Bullseye under a LRN 135 grain bullet split a chamber in the first cylinder load. The quality of steel used in those black powder days can make your reloading effort a mite risky.