The Messerschmitt Me 263 was a rocket-powered fighter aircraft developed from the Messerschmitt Me 163 towards the end of World War II. Three prototypes were built but never flown under their own power as the rapidly deteriorating military situation in Germany prevented the completion of the test program.
The Me 163B had two main shortcomings. One was a limited flight endurance, the second was the lack of a retractable landing gear. The latter meant that the aircraft had to land on a retractable skid. Both shortcomings prevented it from becoming an efficient fighter aircraft.
The Me 163C was an improved design with increased fuel tankage but still lacked retractable landing gear.
The project was then handed over to Heinrich Hertel of the Junkers company. This resulted in the aircraft becoming the Junkers Ju 248.
The design of the Ju 248/Me 263 started after the Me 163C because the Me 163C was not considered an adequate successor to the Me 163B because of its landing skid. The Ju 248/Me 263 took the wings and tail section of the Me 163B while the Me 263 was a completely new design.
Source - Wikipedia