The Lyman 2nd edition book shows that 473AA is similar to Unique and Herco powders when used in 12 gauge 1 1/8 and 20 gauge 7/8 loads. I don't see any uses for magnum or "back fence" loads. CAUTION! Nothing I can find shows that 473AA is a direct replacement for 500HS, but seems to be similar.
Best to consult with Hodgdon who is distributing the Winchester line of powders.
Hope everyone who has helped with the above info shoots well.