Nothing factual, just speculative. Why the name change? Was this like doing business under a new name or more of a political expression? I think it the latter. The name of the Andrew Jackson Guards (Horseshoe Bend is in Tallapoosa County) did not represent the new political reality in 1861. It may have sounded too "cooperationist" as Jackson was well known to have opposed earlier murmerings about secession. The Tallapoosa Rifles, well, that sounds a little more belligerent.