Approximately 5,000 Civil War Model 1861 rifled muskets were converted at the Springfield Armory in 1866. It soon became apparent that many of the small working parts in the breech system were not going to have a long service life, and the action was too complicated for normal service use. Therefore, before the Model 1865 production order was completed, a less complex rifle was already being tested. This caused the Model 1865 to be called the "First Allin", and the following revised model, the Springfield Model 1866, to be called the "Second Allin".