There are many different type and size of artillery existed during the first world war, however none of them could even come close in range to the famous Paris Gun. The gun was named after the city it was built to bomb from far behind the German lines. The plan was that by bombing Paris would break the moral of the people and by that the French government would sue for piece. This was the first time that a weapon was built for exclusively terrorising civilian population in the modern military history. Yes i know about the Zeppelins and their bombing campaign but those also were used against military targets. They were in service from March to August 1918. When the guns were first used, Parisians believed that they had been bombed by a high-altitude Zeppelin, as the sound of neither an airplane nor a gun could be heard, which was not unheard of as German Zeppelins conducted bombing raids with their engines off over cities, so they were difficult to spot in the night.
The Paris Gun was the largest pieces of artillery used during the war by barrel length, also we can safely say that this was the gun that had the longest firing range ever seen combat and was not using a self-propelled ammunition.
As military weapon, the Paris Gun was not a really good weapon. The payload was small, the barrel required frequent replacement, and the guns' accuracy was good enough for only city-sized targets. Due to the low accuracy it was not a good tactical weapon, and due to the low payload, it was not a great strategic one.
As the Paris Gun was destroyed by the German Army in the face of the final Entente offensives, we don't know exactly what it was capable if. Each resource states slightly different data for the weapon's size, range, and performance. However a note on the gun was discovered written by Dr Fritz Rausenberger who was the engineer on charge when the gun was developed which clarified most of the confusing data.
The gun was capable of firing a 106-kilogram shell to a range of 130 kilometres and a maximum altitude of 42.3 km. This was the greatest height reached by a human-made projectile until the first successful V-2 flight test in October 1942. The distance from the gun to the target was so far that the Coriolis effect was substantial enough to affect trajectory calculations This means that the gunner had to take into consideration the rotation of the planet under the bullet and modify the angle of the gun accordingly.
To build such a gun they used worn out 380mm gun barrels from another large artillery called “Langer Max” that were fitted with an internal tube that reduced the caliber from 380mm to 210mm. The main section of the barrel was 21 metres long but it also had an extension so it reached around 31 meters long. Due to this length could not support it’s own weight hence a suspended support was needed to keep up the barrel. Interestingly as it was based on a naval weapon, the gun was manned by a crew of 80 German Imperial Navy sailors under the command of Vice-Admiral Maximilian Rogge. When it was used, it was surrounded by several batteries of standard army artillery to create a "noise-screen" around the big gun so that it could not be located by French and British spotters.
The Gun fired a 106kg heavy projectile that had a diameter of 216mm and the length of 960mm. Even though the projectile was fairly large, the explosive was only 7kg in it. This was due to the enormous forces the bullet had to withstand when it was fired to prevent premature explosion in the barrel. Once it reached the target, it created crater around 3-4m wide and around 1,5 meter deep.
As a huge amount of explosive was needed to launch every projectile, each shot wore away a significant amount of material from the inside of the barrel. Hence the manufactured shells were increasing in diameter and were numbered which shell to load for the first shot, then a bit bigger one for the second and so on. Also after each shot the barrel was measured to add extra propellant to the next load to fill the gap that was wore away. Each barrel could only be used around 65 times then they had to be sent back to the factory to be rebored and manufacture new shells for them.
The first time this gun was used on 23rd of March 1918 and shot around 21 times. As at the time the French Army and the population of Paris couldn't imagine that the bombardment is from an artillery piece, they assumed that these were bombs from a very high-altitude Zeppelin bombing the city. However once shell casing from the explosion sites were collected, they have established that these are from some sort of artillery, so they searched the nearby hills and quarries for a hidden German gun. Few days later using reconnaissance planes, the French was able to establish the locations of the guns and some of them was bombarded via artillery, and some using bombers. But this did not stop the German army to carry on with their bombardment. The number fired shells during the campaign was between 320 and 367 but its not easy to establish this due to the conflicting sources.
In August of 1918 the gun was pulled back to Germany due to the Entente advancement. When the war was over, although the Allied forces demanded the gun to be turned over, all of them were destroyed and only a carrying case was confiscated.
The Paris Gun was indeed an engineering marvel, the first ever truly long-range strategic weapon, however the cost of this project compared for the return was not in line and it was not successful. It was inaccurate, expensive, slow and delicate, in the meantime it did not achieve its goal to break the moral of the civilian population.
