The Remington New Model Army is available from the mystery box in the Zombies map Buried. It is functionally similar to the Python, but with the ability to reload all six rounds at once, and having higher chest and head multipliers when Pack-a-Punched.
When stored in the Weapon Locker in Buried, it becomes a Python (or a Cobra, if it is Pack-a-Punched) in TranZit and Die Rise. If a Python is placed in the Weapon Locker and taken out in Buried, the reverse occurs.
When Pack-a-Punched, it becomes the Sassafras and is effective until rounds in the 40s. The cylinder size is doubled to twelve rounds and reserve ammunition is increased.
The Remington New Model Army is also seen in the hands of Tank Dempsey during the introduction scene on the map Origins, despite not being available to players on that map.