Defense tech startup Mach Industries has raised a fresh $600 million in capital in a Series C extension round that has doubled its valuation to $3.7 billion, the company announced on Thursday. It announced the original Series C in June, which was $300 million at a $1.8 billion valuation. Investors in both tranches include Ribbit Capital, Infinite Capital, Bedrock Capital and Sequoia. That means that this raise represents a two-fold jump in just three months. The previous round was also a big inc...