It is not a given to say that "rifles were later produced weapons from the 1850's." Many early smoothbore muskets (US and foreign) were later rifled. So it's possible the "German rifles" referred to were old smoothbores (perhaps as old as 40 years) that had been rifled, hence replacing them with the newer Lorenz was considered an improvement. As to replacing the Enfield with the Springfield, the Springfield was the standard issue arm of the US and had interchangeable parts, something which the contract Enfields sorely lacked.

John Gross