Very interesting video on the H&K G11.
I knew a bit about the history and development of this gun but never researched the entire story nor have I ever done any looking into how the internals worked. This video goes into fantastic detail on the history and working of one of the most unique firearms in modern history. (Not to mention a favorite in Fallout 2)
The G11 was a combined effort by H&K and Dynamit Nobel to produce a new rifle for the German military with truly new technology. The core of the system was the use of a caseless cartridge developed in the late 60s and early 70s by Dynamit Nobel, which then allowed H&K to design a magnificently complex action which could fire three rounds in a hyper-fast (~2000 rpm) burst and have all three bullets leave the barrel before the weapon moved in recoil.
Remarkably, the idea went through enough development to pass German trials and actually be accepted for service in the late 1980s (after a funding shutdown when it proved incapable of winning NATO cartridge selection trials a decade earlier). However, the reunification with East Germany presented a reduced strategic threat, a new surplus of East German combat rifles (AK74s), and a huge new economic burden to the combined nations and this led to the cancellation of the program. The US Advanced Combat Rifle program gave the G11 one last grasp at a future, but it was not deemed a sufficient improvement in practical use over the M16 platform to justify a replacement of all US weapons in service.
The G11 lives on, however, as an icon of German engineering prowess often referred to as "Kraut Space Magic" (in an entirely complimentary take on the old pejorative). That it could be so complex and yet still run reliably in legitimate military trials is a tremendous feat by H&K's design engineers, and yet one must consider that the Bundeswehr may just have dodged a bullet when it ended up not actually adopting the rifle.