Drop In Conversion Cylinder for the 44 Cal Ruger Old Army. 6 Round, Stainless 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. The cylinder features small windows on all chambers. The windows help identify which chamber is loaded or not. The hammer is placed on an empty chamber.