The Ruger Single-Six is a single action rimfire revolver produced by Sturm, Ruger. The Single-Six was first released in June 1953. The Single-Six is currently produced as the New Model Single-Six. The term "New Model" simply means that this model includes Ruger's transfer bar mechanism for increased safety, allowing one to carry the revolver safely with all 6 chambers loaded. Prior to 1973, the Single-Six was produced without the transfer bar mechanism, making it less safe to carry with all six chambers loaded, and with the hammer resting on a loaded chamber. The transfer bar safety allows the weapon to fire only when the trigger has been pulled. Ruger provides the transfer bar safety upgrade free of charge for owners of any old model Single-Six.