One of the earliest bolt action rifles was developed by brothers Paul Mauser and Wilhelm Mauser. At that time a U.S. patent could not be obtained if a foreign one had already been filed, so they filed a U.S. patent first, before filing in Germany. The patent lists their home as "Oberndorf on the Necker, in the Kingdom of Wurtemburg", and was issued in 1868. This was a single shot rifle, and shot an 11 mm bullet. The next big improvement would be the introduction of a magazine and repeating bolt action rifles.