In the old and older revolver sub-forums members continually post that WW II British .38 S&W cylinders converted to .38 Special by reaming them deeper make the .38 Special cases swell so bad that those revolvers should be avoided and have little value. A cylinder reamed to accept 9 mm makes .38 Special brass swell just as bad. Also making the 9 mm bullet pass unsupported through the .38 Special chamber before entering a too loose chamber throat then a too small bore is not going to improve accuracy. However, I have no doubt the 9mm bullets will still be accurate enough to satisfy a 5 yard expert.

BTW, S&W extractor rods are not strong enough to extract 5 steel 9 mm cases at once so you will not be able to use the least expensive 9 mm cartridges.