Somewhat amused by this as Elmer Keith was driving 44 Magnum 240gr boolits to 400 yards with accuracy out of a 4" revolver. Getting a .357 mag to shoot at 100 yards should be a walk in the park!
Personally I would use a heavy round nose around 170gr (I have a lovely 6 cavity Hensley and Gibbs mould) driven by a healthy load of Alliant blue dot or Viht equivalent (340 I believe). Good shooting.