There’s some interesting information over at Gwinn Firearms about this 1970s conversion of the M16 rifle by Bushmaster, which was tested by the Air Force to give downed pilots a little more punch and range than a ordinary handgun can afford. Component diagram:

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Additionally, here’s a video link I found, which shows the pistol in operation. [...]

Modern digital camouflage has a Cold War origin in experiments conducted in the late 1970s by the United States Army.