Please don't parrot what you have "Heard somewhere" and have no experience with. The nominal difference between .38 Spl. and .38 S&W is .008", about 4 pages in a typical "slick" magazine. The smaller case will have a slightly higher probability of splitting when fired than a proper sized case, but to say it will split is assuming what simply isn't true.

One of the most extreme cases I can cite is fire-forming 7mm Remington Magnum cases to .458 Winchester Magnum, a difference of ca. .174", nearly 22 times the difference between the .38 cases, with less than 5% failures due to splitting. If anything was going to split this would seem to be a nearly 100% certainty, wouldn't it?