Herco was listed in old manuals as a powder for fac dup loads
and is still in modern manuals.
Some data calles for a magnum primer and some for a standard primer...............I have not used this powder, but being between Unique and Blue Dot I can see why both primers might be used in data.
Probably a great powder for heavy bullets and medium to heavy loads.

Hope you post later on what type primer worked best for you..............have a great time with the powder.