coach guns are similar to sawn-off shotguns but differ in that coach guns manufactured after 1898 are offered as new with 18" barrels and 26" overall length and meet legal requirements for civilian possession in the united states. australia and new zealand have slightly different laws for length, with nz requiring a minimum overall length of 30" (anything shorter is considered a pistol) with no minimum barrel length and australia requiring an 18" barrel and a 30" overall length. in the united kingdom, however, shotguns must have a minimum barrel length of 24" to be eligible for ownership on a shotgun certificate, and shotguns with barrels under this length (which includes coach guns) must be obtained on the more stringent firearms certificate. some modern coach guns feature internal hammers as opposed to the traditional external hammers.