How much powder?

[handgun357]

How much Winchester 231 powder for 38sp casing with 125 grain jacketed hex hollowpoints? My "Lee" manual has no reference for that peticular projectile using Wichester 231.
Also do you really need magnum primers for .357mag rounds?
I have always used regular small caliber pistol primers.
What exactly is the difference?

 

[Sample]

My Speer Reloading Guide shows 5.6 grains under a 125 grain bullet. It produces 944 fps from a 6" barrel. It does NOT specify magnum primers.