John, if those Snakebites are made of soft lead, they'll obdurate to the right size, which I think is in the .361" range, if my (admittedly crappy) memory serves. A Hollow-base bullet for standard 38 Spl. or 357Mag. loading will be ideal, however, as I said, my .355" size bullets (supposedly for 9mm loads) - while not correct - DID fill the grooves, even using BP.
Wiki has a decent blurb on the 38 S&W and the specs are listed.
.361" is the correct bullet size.