The RUGER® DEERFIELD® CARBINE relies upon the gases produced from the fired cartridge to cycle the action and is chambered only for the .44 Magnum cartridge. It should not be used with any other .44 caliber ammunition, such as the .44 Special. Most .44 Magnum ammunition factory loaded to U.S. industry specifications is suitable for use. However, “Medium Velocity” nonjacketed ammunition may not produce the volume of gas necessary to consistently cycle the action or give optimum accuracy and is not recommended. Do not use lead bullets -- they will clog the gas port in the barrel and prevent proper action cycling. Aluminum-cased ammunition should not be used, as it may stick in the chamber when fired, resulting in extraction and functioning problems. .44 Magnum cartridges with bullet weights below 215 grains are generally not compatible with the Ruger Deerfield Carbine, and those with bullet weights above 255 grains generally exceed the maximum overall length of 1.610” allowed by U.S. Industry Standards and may not fit into the magazine. Such cartridges at either end of the spectrum of .44 Magnum ammunition loadings should not be used in the Ruger Deerfield Carbine.