The Kerr's Percussion Revolver was (and remains) a difficult firearm to classify, with many refering to it as a single action revolver, while others may refer to it as being double action. This confusion arose because the earliest Kerrs were produced with an overly complicated double action mechanism (it is plausible that this mechanism was based on designs by Kerr's cousin, Robert Adams), which required constant maintenance and was prone to failure. The majority of Kerrs, however, were produced with a single action mechanism, requiring the hammer to be cocked manually by the shooter and were, as a result, far easier and cheaper to produce and use.