False.
From http://www.nramuseum.org/the-museum...rpers-ferry-model-1842-percussion-musket.aspx :
The Model 1842 was the first regulation percussion musket to be manufactured at both Springfield and Harpers Ferry Armories, as well as the first to be produced by both national armories with fully-interchangeable parts. These were also the last .69 caliber smoothbore arms to be produced by the U.S. government