Here is a new idea for a battle rifle that was built in a Colorado garage. It has some nice features, and a very different design.
Picture from this article:
The only thing I would change, is I would add heat sinks to both sides of the bores. The rate of fire is crazy, as you can Not feed that beast! The six mm size is a step in the right direction, as we have a military bullet that is entirely too small for warfare!