Heckler&Koch G11 Assault Rifle (technically not a prototype, never got any contract) designed 1968 - 1991
top picture - G11K2 middle pictures - G11K1
4,73x33mm, 90 rounds capacity, Deutsche Qualität, etc The most distinctive feature of that gun, thought as a replacement for the G3 in West Germany, is its use of caseless ammunitions. The ‘cartridges’ were made of formed propellant/primer, with the bullet cozily burrito’ed inside. The gun achieved nerd-wide recognition for its futuristic, cold war space age design.
When the Germans invented the Sturmgewehr 44 during World War II, it was the most advanced production small arm in the world which would inspire a revolution in military firearms. However, Germany was not quite done yet. In the waning months of the war Germany experimented with a new design called the Sturmgewehr 45, which was created to be a further improvement of the STG 44. The new STG 45 was similar in many respects to the earlier STG 44. It used the same 30 round magazines, was chambered in the 7.97x33 Kurz cartridge, and visually both rifles look similar. However the STG 45 utilized a new roller delayed blowback design similar to the MG 42. I will not pretend to understand how such a mechanism works, but I believe it has something to do with magical German elves.
In addition to its new operating mechanism, the STG 45 was designed to be produced using faster manufacturing processes, cheaper materials, and lighter materials. The earlier STG 44 cost approximately 75 reichmarks to produce, however the STG 45 was significantly cheaper at 30 reichmarks. While the STG 45 was being designed, Germany was badly losing the war and suffering from severe raw material shortages while its industrial infrastructure was being bombed to dust. Thus a cheap assault rifles that required little manpower or resources to produce was desperately needed. Germany was defeated, however, before testing of the weapon could be finalized and production could begin. Parts for 30 rifles were produced, which weren’t assembled until after the war, mostly done by Allied powers who seized the weapons for experimentation and testing.
After World War II the designers of the STG 45 moved to France and continued work on their designs. The design would become inspiration for the Spanish CETME rifle and the Heckler & Koch G3.