The Landmark conversion refers to a modification of the Norwegian

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 kammerlader

Kammerlader

The Kammerlader, or "chamber loader", was the first Norwegian breech loading rifle, and among the very first breech loaders adopted for use by an armed force anywhere in the world. A single shot black powder rifle, the kammerlader was operated with a crank mounted on the side of the receiver. This...

 rifle

Rifle

A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

s to allow them to fire rim fire ammunition, as opposed to being caplock weapons. It was invented by Jens Landmark

Jens Landmark

Jens Landmark was a Norwegian military officer and politician. He reached the rank of Lieutenant Colonel, was the director of Kongsberg Weapons Factory from 1854 to 1880, invented the Landmark conversion and served both as mayor as well as three periods in the Norwegian Parliament.-Personal...

.

The mechanism of the Landmark cartridge conversion is brilliantly simple. The chamber

Chamber (weaponry)

In firearms, the chamber is that portion of the barrel or firing cylinder in which the cartridge is inserted prior to being fired. Rifles and pistols generally have a single chamber in their barrels, while revolvers have multiple chambers in their cylinders and no chamber in their barrel...

, which on a kammerlader is a separate piece tilted up and to the rear, is opened as before, but can be tilted further backwards by means of a hinge in the middle of the chamber. The 12.17 x 44 mm

12.17 x 44 mm

The 12.17×44 mm rimfire round was developed by a joint Swedish-Norwegian committee in 1867. The goal was to create a round of ammunition that would not only work in the new rifle then under consideration , but also would be suitable to use in old, converted kammerlader rifles.The round, nominally...

rim fire cartridge is placed backwards, facing the shooter, before everything is rolled back forward. The only part to be modified was the chamber and a curving firing pin was added where the nipple for the cap had been. Pictures showing the Landmark conversion can be found here