Well, according to the site you posted max load is 3.7 grains, and according to this site 4.7 grains is max.
http://www.handloads.org/loaddata/de...rce=Winchester
Since there seems to be so much inconsistency among sources, what I'm looking for is a load that works well (in practice not from a book) using 231 and 158 hardcast to simulate you average store-bought .38sp.