How about SWAT in big letters, with "On The Firing Line" underneath. Over time, make the SWAT smaller and smaller, and The Firing Line bigger and bigger, until you officially change the name to The Firing Line. That way you don't lose any of the long time readers.
Personally I kind of like On The Firing Line, so the magazine could be OTFL and the website will always be TFL.
Or my second choice: American Thunder Gunnut Tactical Action Shooting Monthly.