George Nonte, in Handloading for Handgunners, writes about his experiments with 357 magnum in short barrels. The conventional wisdom is that 357 magnum from short barrels is not much faster than 38 special. He says you can correct this to some degree by using a faster powder, like Unique or Bullseye. This is because the 357 factory ammo is usually designed for 6" barrels, and uses slower powder than is appropriate for 2" barrels.