Okay, I got my hands on Paris Kanonen - The Paris Guns (Wilhelmgeschütze) and Project HARP by Gerald Bull (yes, that Gerald Bull) and Charles Murphy through a friend with access to a university library, and it's a fascinating read with original research and fantastic translated primary source documents by Fritz Rausenberger and others. It's leagues ahead of open-source accounts like Colonel Miller's writings and tertiary sources about the subject, along with cutting-edge analysis by arguably the world's foremost expert on ultra-long range artillery.
This being Secret Projects, I want to point out two specific unbuilt designs for the Paris Gun: incremental improvements to the Paris Gun extending its range and caliber before all progress was halted and eventually destroyed after WW1 ended, and a proposal for a saboted sub-caliber munition fired from a regular 35/35.5cm gun.
So the first designs are the less interesting one, and I believe all we have left are the few notes by Rausenberger at the very end of his account of the Paris Gun program. Basically, these two incremental design improvements were:
Now, Rausenberger is very sparse on the details here, and no designs or other writings exist as far as I know that corroborate Rausenberger's claims for these improvements. That being said, he's basing these improvements off extensive testing at Meppen and real-world experience firing the cannon, so I imagine there still is significant merit to his claims. Naturally, none of these improvements actually happened, since the war ended and the Entente disarmed Germany.
The more interesting proposal for the Paris Gun is the proposal of von Eberhard, apparently the person in charge of all external ballistics research at Krupp. As Rausenberger recounts, von Eberhard wanted to use the Krupp 35.5cm/L52.5 gun to fire a modified 210 kg shell with 35.5 cm bands and a 90kg 21 cm shell in the middle of these bands. The bands would fall off the 21cm shell due to the drag difference, but the 90kg shell with a much-reduced drag would continue on with an initial firing velocity of 1500 m/s and hit targets at ranges in excess of 100 kilometers (pg. 26-27).
Although he admitted the concept was theoretically sound, Rausenberger rejected this proposal for three perceived reasons:
As such, Rausenberger went with the conservative option of a superlong 21cm barrel that became the Paris Gun as we know it.
However, Gerald Bull ran computer simulations based on scaled 1980s 175mm saboted shell design for the Eberhard proposal designed to match the specifications of the 35.5cm L52.5 gun and the RPC/12 propellant available to the German WW1 project. He also scaled down the shell slightly from 210 to 200mm (pg. 77).
Here's the modelled shell (pg. 78):
What he found was that the designed shell was able to carry 17kg of high explosive filling, nearly 2.5 times as much as the 210mm shells used for the built Paris Gun, and was able to reach 126 or 121 km for breech pressures of 350 and 330 MPa respectively (pg. 78). The 350/330 MPa breech pressure was significantly less than the 450+ MPa breech pressures of the built Paris Gun, meaning that barrel life could have been measured in the hundreds of rounds instead of the dozens. Combined with the fact that the saboted round didn't need a massive barrel extension, and von Eberhard's proposed gun could have been an order of magnitude more effective and deployed in larger numbers (maybe even used as a naval round, although I'm not sure what would be its effectiveness).
Also, sabot dispersion was relatively close to the gun, so as long as the gun was not right behind German trenches, it would not have posed any threat at all to German troops.
The caveat here is that Bull is transposing a 1980s 175mm projectile design onto von Eberhard's proposal for his calculations, resulting in both a much lighter sabot (only 37.7 kg vs 110 kg) and a significantly heavier shell (118 kg vs 90kg) than the proposed design, so without the advantage of hindsight, the actual saboted shells would be notably less effective. They could still hit at 100km ranges and bring a larger HE payload to the target though without substantial modification to existing naval guns though, based on von Eberhard's calculations that proved to be generally accurate for the actual performance of the Paris Gun.
Personally, I doubt that either improvement would alter the fate of Germany aside from making the French slightly angrier as more of Paris is destroyed, but a proof-of-concept that saboted munitions work if von Eberhard's design was greenlit could accelerate their development and see mature APDS shells used at the start of WW2.
Any thoughts on these Paris gun proposals?
PS: this is my first major post, so let me know if I did anything wrong.
This being Secret Projects, I want to point out two specific unbuilt designs for the Paris Gun: incremental improvements to the Paris Gun extending its range and caliber before all progress was halted and eventually destroyed after WW1 ended, and a proposal for a saboted sub-caliber munition fired from a regular 35/35.5cm gun.
So the first designs are the less interesting one, and I believe all we have left are the few notes by Rausenberger at the very end of his account of the Paris Gun program. Basically, these two incremental design improvements were:
- A 3-meter smoothbore extension to the existing Paris Gun design and the employment of boat-tailed shells to increase the range of the guns to 142 km (I assume for the initial shots; barrel wear would quickly shorten the distance of these shots)
- A brand new system firing 305mm shells weighing 300kg up to 170km, along with improvements to reduce barrel wear.
Now, Rausenberger is very sparse on the details here, and no designs or other writings exist as far as I know that corroborate Rausenberger's claims for these improvements. That being said, he's basing these improvements off extensive testing at Meppen and real-world experience firing the cannon, so I imagine there still is significant merit to his claims. Naturally, none of these improvements actually happened, since the war ended and the Entente disarmed Germany.
The more interesting proposal for the Paris Gun is the proposal of von Eberhard, apparently the person in charge of all external ballistics research at Krupp. As Rausenberger recounts, von Eberhard wanted to use the Krupp 35.5cm/L52.5 gun to fire a modified 210 kg shell with 35.5 cm bands and a 90kg 21 cm shell in the middle of these bands. The bands would fall off the 21cm shell due to the drag difference, but the 90kg shell with a much-reduced drag would continue on with an initial firing velocity of 1500 m/s and hit targets at ranges in excess of 100 kilometers (pg. 26-27).
Although he admitted the concept was theoretically sound, Rausenberger rejected this proposal for three perceived reasons:
- He thought the separation of the sabot and the shell could not happen smoothly and would result in severe distortions to the shell trajectory.
- He believed the 90kg shell was too light to have any substantial impact
- He was concerned that the sabot would hit the ground amid German lines and endanger troops.
As such, Rausenberger went with the conservative option of a superlong 21cm barrel that became the Paris Gun as we know it.
However, Gerald Bull ran computer simulations based on scaled 1980s 175mm saboted shell design for the Eberhard proposal designed to match the specifications of the 35.5cm L52.5 gun and the RPC/12 propellant available to the German WW1 project. He also scaled down the shell slightly from 210 to 200mm (pg. 77).
Here's the modelled shell (pg. 78):
What he found was that the designed shell was able to carry 17kg of high explosive filling, nearly 2.5 times as much as the 210mm shells used for the built Paris Gun, and was able to reach 126 or 121 km for breech pressures of 350 and 330 MPa respectively (pg. 78). The 350/330 MPa breech pressure was significantly less than the 450+ MPa breech pressures of the built Paris Gun, meaning that barrel life could have been measured in the hundreds of rounds instead of the dozens. Combined with the fact that the saboted round didn't need a massive barrel extension, and von Eberhard's proposed gun could have been an order of magnitude more effective and deployed in larger numbers (maybe even used as a naval round, although I'm not sure what would be its effectiveness).
Also, sabot dispersion was relatively close to the gun, so as long as the gun was not right behind German trenches, it would not have posed any threat at all to German troops.
The caveat here is that Bull is transposing a 1980s 175mm projectile design onto von Eberhard's proposal for his calculations, resulting in both a much lighter sabot (only 37.7 kg vs 110 kg) and a significantly heavier shell (118 kg vs 90kg) than the proposed design, so without the advantage of hindsight, the actual saboted shells would be notably less effective. They could still hit at 100km ranges and bring a larger HE payload to the target though without substantial modification to existing naval guns though, based on von Eberhard's calculations that proved to be generally accurate for the actual performance of the Paris Gun.
Personally, I doubt that either improvement would alter the fate of Germany aside from making the French slightly angrier as more of Paris is destroyed, but a proof-of-concept that saboted munitions work if von Eberhard's design was greenlit could accelerate their development and see mature APDS shells used at the start of WW2.
Any thoughts on these Paris gun proposals?
PS: this is my first major post, so let me know if I did anything wrong.
