Ethan Thornton dropped out of MIT at 19 to build weapons. The first one, a hydrogen-powered system he prototyped with parts from Home Depot and Amazon, didn’t work out — “hydrogen was just a bad bet in general,” he told me this past week at TechCrunch’s StrictlyVC event in Los Angeles. Three years later, his company, Mach Industries , is running six weapons programs and earlier this month closed a $300 million Series C round at a $1.8 billion valuation. The startup has now raised roughly $485