The number 209 refers to a size and the "A", or other markings refer to a version. A different version usually means a different formulation of priming compound. Primers may differ significantly between versions and have their own unique loading data. Also, while 209 refers to a size, there may be a minor difference in actual size between manufacturers.
One thing I have noticed is that the material of the primer body may change (i.e. from brass to aluminum) while the primer version does not change.
Be sure to use the correct loading data for each primer. For example, a Federal 209 is different from a Federal 209A.
One thing I have noticed is that the material of the primer body may change (i.e. from brass to aluminum) while the primer version does not change.
Be sure to use the correct loading data for each primer. For example, a Federal 209 is different from a Federal 209A.