Drop in Conversion Cylinder for the .44 Cal Pietta 1858 Remington Army. 5 Rounds, Steel. Converts .44 caliber black powder revolver to shoot 45 ACP round. Use only cowboy ammunition that does not exceed 850 FPS; never use hot or jacketed ammunition. 5 Safety Stop notches located between chambers. This feature allows the hammer to be lowered between loaded chambers.