Federal Shotshell Primers

The 209A is a "hotter" primer than the standard 209. The 209A is the only Federal shotshell primer that has been available as a component for years. Never substitute a 209A in a recipe that doesn't specify list it.

Ditto on what rule303 said. Look carefully at the load data for whether the recipe calls for a Federal 209 or 209A. The 209A is much hotter than the old 209 and will likely raise the peak pressure considerably over what a recipe calls for using the old 209 primer.