This comes up quite often with the majority absolutely certain that you cannot fire .38 S&W in a .38 Special. It all depends on which side of tolerance the .38 S&W you have is.

The last I tried this I had 12 revolvers in .38 Spl. and .357 Magnum (all S&W!). The .38 S&W ammunition I had on hand would chamber in 7 of the 12 or 58%. Do not say it will not work, it will quite often. If it will chamber in your gun it is absolutely safe, if it won't then the question is moot.