Have you gone to Winchester's web site to see if they have loading data?
Most of the manufacturers of powder and bullets publish recipes for their products.
Good luck
Lost Sheep
edit: I checked Winchester and didn't find recipes right away. Oops. They either don't have them or they are buried deeper than I thought.
edit 2: Hodgdon makes Winchester gunpowder and they have some load data that might be helpful.
http://data.hodgdon.com/cartridge_load.asp