In addition to the Speer # 14, you can pick up a Hodgdon basic reloaders manual. They are free at most stores where you can buy powder. It contains a pretty big section of Cowboy Action data both for pistol and carbine. It will be very helpful specially if you will be using Trail Boss, the powder Hodgdon designed for cowboy action shooting.
I like to pick up several ... then compare between them. Never rely on just one IMO. I have three main ones : Hornady, Speer, and Lyman's newest reloading manuals. Plus now we have on-line resources to check as well. If all 'agree' then most be an 'okay' load .