Frank:
The organizational structure you mention was for four 6 pounder field guns and two 12 pounder field howitzers, all bronze smoothbore pieces. This type of mixed battery grew out of the expericiences of the Mexican American War. It was a pre-civil war structure well known in the army and mentioned in all of the artillery manuals. These batteries would not have been a source of the confusion which were more likely caused by soldiers unfamiliar with the cannon.
Ron