I suggest that you call someone from Hogdon as they handle Winchesters powder now and ask one of there techs. by phone or by E-mail. Go to Hodgdon.com to find their website. Good luck and Break-em all. Jeff
My winchester ball powder loading data booklet first edition, dated June 1973 tells; "473AA powder replaces (AA20S and 500HS). It is the same powder as used in double A 20 gauge factory loads. It has a wide range of applications from 12 to 20 gauge". Shoot well.
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.
Having loaded a bunch of 473 I can assure you it has nothing to do with Winchester 500.. Here are a few loads out of the Lyman #1 book.. Field load 500HS..30 grains.. 1 1/4oz shot.. Federal paper or plastic case.. Federal 209 primer.. One Federal pellet protector 7/8" size.. 8800 LUP 1250 fps.. This was a starting load..
Winchester Compression formed case.. 28.3 grains 500HS Winchester 209 primer 1 1/4oz shot.. Winchester AA wad #WAA12 9800 lup 1220 FPS
Remington All American case.. Alcan 220 Max fire primer.. 23.5 grains of 500 HS powder Remington Power Piston #W29926 wad.. 1 1/4oz shot 9600 LUP.. 1165 fps..
With 3" 12 gauge shells there are alot of loads for 1 3/8oz.. There is NOTHING.. I repeat.. nothing.. for 1 1/8oz.. Not to say it could not work..but it would be similar to using Longshot for 1 1/8oz at 1250 fps.. It can be done.. but it burns to slow for consistent ignition and burn.. I have done it with Longshot.. and the factory told me to STOP.. unsafe..and that was the end of it.. I would ask you to either consider it for 1 1/4oz.. which it was designed for..or maybe swap or trade it for a better powder for your needs..