Kentucky keeps changing its mind about them. Sometimes, rifles have to be at least .40 caliber and pistols at least .44 caliber. Other times, no minimum caliber for rifles but .44 for pistols. Last time I checked there was no minimum caliber for any firearm as long as it was centerfire or sidelock and fired a single projectile. They have always been really strict about no rimfires and no shot loads for deer and larger game tho.