Matt
Longshot would not be my first choice for this gun , most of the data puts the loads in the Ruger ( BH , SBH & RH ) , FA & TC levels as a Mag powder like H110 .
2400 , Titegroup or even Bullseye would better for what you have to work with , i shoot mostly cast in my 45 LCs over Unique and it does a wonderful job .
stimpy