I recently purchased a S&W model 27-2 357,It is stamped 357 only on the barrel, may I also use 38 special rounds for practice?
Don't neglect to give the chambers in the cylinder a good cleaning after shooting a lot of .38 Special ammo, especially if you shoot unjacketed lead. A carbon (and lead) ring will form, after a while, that will not allow .357 magnum rounds to seat properly in the chamber. If it gets dirty enough, it will push a .357 cartridge back far enough to drag against the frame, when the cylinder rotates, and you will think your gun is broke.
Yes you can shoot 38 special, 38+P, and 357 enjoy your gun, model 27's are nice guns.
Listen to Bisley; enough .38s will indeed cause an issue. Otherwise, not to worry, a traditional and very classy .357.