These were not minor innovations. In fact, they were so important that he used them as leverage to get himself out of prison, whereupon he returned to the military--no small feat considering he had been kicked out twice at that point.
His components became the basis for the M1 carbine. Even if you're not a diehard gun-nut scrolling through this article by manipulating your mouse with the butt of a revolver taped to another, larger revolver, you've probably heard of the M1 carbine. It was basically the first iteration of the modern war rifle, and it absolutely revolutionized the way battles were fought from then on. If you think it's a little scary that convicted murderers are allowed to manufacture and sell weaponry to the military from prison, please realize this was truly the best-case scenario. Because when you hear the phrase "invented a new super-rifle in prison" it's usually followed by the phrases "bloodbath the likes of which the world has never seen" and "vowed revenge on Captain America."