The June, 1930 issue of Modern Mechanix has a well-illustrated piece revealing the secrets of the mystery gun that shelled Paris during the Great War a dozen years earlier:
There was a barrel 120 feet in length, approximately twice as long as the biggest guns built to that time — so long, in fact, that the end had to be supported in the air to keep it from bending down and being shot off by its own shell. In fact, that very thing happened to the first of the guns tested at the German proving ground, for the barrel bent a full inch under its own weight.Next they fired a shell 75 to 80 miles or more, over a total trajectory ranging from 90 to nearly 100 miles.
To do that the shell was shot 24 miles above the earth, higher than any man-made thing, save possibly a small sounding balloon, had ever penetrated. At that extreme height the shell traveled through what was almost a vacuum, at a temperature of far more than 100 degrees below zero.
The shell, traveling at an average speed of 30 miles a minute — or sixty times as fast as the usual legal rate for automobiles — took three minutes to complete its aerial flight of 90 miles. It remained away from the earth so long, in fact, that the old world revolved on in space while the projectile was away, so the gunners had to aim a half mile east of the target in order that the target might be there when the shell arrived to hit it.