Perry,
I went back through my notes of when I had a Rossi 357 MAg Lever Action, and the loads I used were as follows.

All with about a 160 grn SWC/GC

6 grns of Unique (A bit similar to our AS-50) avg vel 1262 fps
10 grns of Blue Dot avg vel 1541 fps.
15 grns of 2400 avg vel 1886 fps. (This load is over max in many books, but was OK in my rifle.)

As usual, if you decide to try anyone elses loads, it's your call.

Regards,
David.