I have seen guns made from bronze alloys before, but never an autoloader. Back in 1932 Colt and the Springfield Armory teamed up to test the suitability of using a die cast bronze alloy for gun parts.

The Golden Gun

The gun is exhibited at the Springfield Armory Museum.

In 1932 Springfield Armory experimented with die casting pistol frames and slides from a high tensile corrosion resistant bronze alloy called ‘brastil.’ The resulting ‘golden gun’ represents one of the first attempts to die cast handgun components. Despite the success of the test, the project did not move beyond the experimental stage.

There is a discussion about the pistol at the 1911 Forum.

So the question remains … who is going to be the the first to build a bronze AR-15?

Thanks to Sven for the link.