The thing I find most interesting about that air gun is how modern day writers assume that it was nearly silent. They get that notion from shooting Daisy and Crossman air guns which make very little noise but which also produce very little power. Actually, for any given level of ballistic performance, an air gun makes more noise than a powder gun. Our Crossman pneumatics produce only a fraction of the energy of a .22 short which, from a rifle, makes less noise than the air gun. I seem to recall that the air gun in question had a velocity of less than 1000 fps, made only a loud pop, but a .45 Ml loaded down to subsonic velocity would also make only a loud pop.