Interesting document from a historical perspective, but man, is that description terrible. It's like a nine-year old, raised in a home where english was not the first language, just saw his first Star Wars stormtrooper blaster.
Can we say with confidence what rifle is being described here? A detachable buttstock, a barrel jacket that extends to within 80mm of the muzzle, and a sketch that looks more like a German STG-45(m) than anything else.