This is the V3 London gun. The shell fired by the V3 reached over four times the speed of sound before finally leaving the nozzle. The V3 was a terrifying German weapon designed to shell the British capital from across the English Channel in France.
It was located in Pas de Calais, near the small town of Mimoyecques from which it gets its name. Had it been completed it would have been capable of firing 600 rounds every hour onto London, 24 hours a day, 7 days a week. In order to reach London, the Germans came up with an exotic solution of a multi-chambered cannon.
But was the weapon something that could really work? We have modeled the V3 gun in minute detail to try and answer exactly that. My name is David Webb and this is Blue Paw Print.
The weapon was an incredible 460 feet (140 m) long, allowing time for the shell to be accelerated by high-pressure gases. The barrel had no rifling allowing the shell to reach higher speeds as well as making it easier to construct. Due to its extraordinary length, it had to be built in segments.
The weapon consisted of the barrels and junction sections. On the last 66 feet (20 m) the barrel sections were connected to each other without any junctions. The remaining 32 of these pieces were stacked one after the other which made up most of the cannon’s length.
Connections between pieces were made with thick 16-bolt flanges. The breech was taken straight from the sFH 18, 15 cm (5. 9 inch) field howitzer.
It was a very common weapon produced in the thousands. It featured a locking lever and a pull cord trigger. On each side of the junctions were the auxiliary chambers.
They held solid fuel blocks that boosted the heavy round to a high speed. They were simple in design; the connection to the junctions used the same flange as the barrels. The body was a shortened barrel segment, and the top was a thick welded endcap.
On the cap, a 90-degree screw breech allowed the fuel to be replaced. The gun was angled at 50 degrees on a fixed position aiming at Westminster Bridge in London. Each block of 5 barrel segments had its own steel legs that were embedded into the rock of the tunnels.
We’ll see more about those tunnels later in this film. The V3 shells had a striking resemblance to modern tank rounds, known as Armor Piercing Fin Stabilized Discarding Sabot or APFSDS. The shell fired by the V3 worked in exactly the same way.
The shells came in at a number of different lengths, ranging from 4. 3 feet (1. 3 m) and 172 pounds (78 kg) through to 10.
7 feet (3. 25 m) and 308 pounds (140 kg), but all had the same general design. The elongated shape reduced the effectiveness of spin stabilization, so the round was equipped with fins at the rear that increased the drag at the back and kept the front of the round pointing in the direction of fire.
When the nose hit the target a wooden plunger was pushed into a striker pin that was held back from hitting the primer by a tough spring. Under the shock of impact, the spring compressed and the striker was forced into an ignition fuse. The primed ignition fuse sends a blast down the flash hole where it reaches the main fuse that will, in turn, make the main charge in the middle section explode.
The main high explosive charge was up to 55 pounds (25 kilograms) in the longer versions. Due to the fins, the round did not fit neatly in the 5. 9 inch (150 mm) barrel of the gun.
And the Germans needed to avoid any gas leaks around the shell during the shot. To solve this, the Germans came up with a novel solution. Towards the front of the shell there sat a cast iron cage that surrounded the body of the round with 8 sleds.
These kept the round pointing straight ahead as it slid through the barrel. They were formed with 2 sections that fell off once the shell left the muzzle. At the rear, there was a piston that pushed the finned projectile up the barrel.
This piston had a sleeve that extended down from the rear, without which the piston could not seal the gases behind it, so the gun would not have worked effectively. We’ll take you through exactly how that works later in the film. The round was centered on the piston, with a small male nub that fit into a cup on the rear of the round.
In the center of the piston there was a small hole that funneled gasses from the firing process into a small chamber within the round. This elegantly simple solution ensured the separation of the piston once the round left the barrel. To fire the cannon the shell with the sabot would've been inserted into the breach, followed by by the powder charge, and then a standard German 15 cm howitzer casing.
The breech was slid closed, the tunnel was confirmed clear, and then the safety would be turned to the firing position. Inside the breech, this action turned a shaft which cleared the firing pin to move. Then the firing cord was pulled.
As the cord was pulled, the striker would be pushed back, compressing the spring. Once it passed the threshold, the striker was pushed forward by the spring and hit the primer on the casing. The chemicals inside the primer exploded on impact, lighting the rest of the propellant charge.
The pressure filled the piston, expanding its sides and making a perfect seal against the barrel. At the same time, gases entered the cavity in the rear of the shell. The shell then moved up the gun until the first auxiliary propellant charge.
The extended skirt of the piston ensured the gases would only release once the fins had cleared the opening. Once they did, the hot gases would enter into the auxiliary chambers where they lit the fuel. The fuel burned and feed more pressure into the barrel.
This process would be repeated all the way up the barrel, passing 32 pairs of charges and reaching over 4 times the speed of sound before the shell finally left the muzzle. Once released the forward sabot fell off, and at the rear the gases in the small chamber pushed the piston away from the round. The shell would now be fully released in its flight towards London.
Back within the breech, an internal spring reset the firing mechanism, allowing the system to be fired again. The entire weapon was mechanical. Electrical timing of charges was discarded as an option early in development due to its complexity.
While the cannon itself was relatively simple, what was required to use it was not. Due to its complete inability to move, the weapons and their crew needed exceptional protection. That was the duty of the Mimoyecques Fortress, a massive underground bunker built exclusively for the London Gun.
Built on a hill, the complex reaches 350 feet (106 m) underground, and it is made out of a network of tunnels. Its most striking feature was five angled tunnels intended to house the guns, named “drifts”. They are set at 50 degrees and each of the 5 V3 guns would have been stacked one on top of the other.
To protect the drift openings they were surrounded by a massive concrete pad 18 feet (5. 5 m) thick, and covered with 7. 9-inch (200 mm) thick steel plates.
The plates featured holes for the shell to fly through and would act as the muzzle of the cannon. The plan called for 5 drifts in a single bunker, with a second bunker built nearby wuth another 5. The largest underground section was 98 feet (30 m) below the surface.
It featured an underground railway station to feed supplies to the fortress. A railway line was built to supply the complex and it went underground through the ravine on the side of the hill. A separate network of rails was used during construction to move mining carts, but later it was designed to support movement of shells, charges and supplies all around the complex.
To the west of the railroad was a grid of 13 galleries. Galleries 3 to 13 are perpendicular to the railroad and serve as passageways. They all have rails for minecarts which were used to extract rock during construction, but they would have presumably also been used to move materials and ordnance during operation.
They’re all connected by Gallery number 2 which was used to move personnel and equipment between each gallery. The center galleries, 6 to 10, continue past Gallery 2 and connect with the drifts. Personnel would’ve used these openings to reload the auxiliary chambers between firings.
Gallery number 1 connected the central galleries and featured four elevators that brought personnel and ammo down to the lower levels. Connected to Gallery 1 are additional chambers for a water tank, engines, and a makeshift workshop for use during construction. We think the same workshop would have been used for routine maintenance and minor repairs when the guns were operating.
On the other side of the railroad, there were meant to be living and administrative quarters, of which few were built. On one end of Gallery 2 a separate tunnel provided foot access to the fortress, along which there were more living quarters. Between 1000 and 1200 people would’ve manned the bunker during operations.
The further 7 shafts stretched to the surface to bring air into the massive compound. Shafts 3 to 6 ventilate Gallery 2, while Shafts 7 to 9 ventilate the railway tunnel. Shafts 1 and 2 go down from Gallery 2 to an unnamed gallery 203 feet (62 m) underground.
The gallery connects to the drifts and its main purpose was the ventilation of the drifts to deal with the fumes after firing. It also could’ve been used for maintenance and as access to reload the auxiliary chambers, but it’s not known for certain. At the very bottom at 350 feet (106 m) underground, a gallery connected the ends of the drifts.
The loading of the shell and the firing of the weapon would’ve occurred here. Operating the weapons would’ve been arduous and fast-paced. After each firing personnel had to enter the drifts to manually reload every single auxiliary chamber of the 5 guns.
So the men would’ve had to move quickly across stairs while carrying the fuel cylinders. The majority of the chambers would be supplied by ammo hoists moving on the rails over the guns. Refueling an auxiliary chamber involved unscrewing the hot breech, potentially dusting off the inside to prevent embers from igniting the fuel in the operator’s face, pushing the fuel into place, and retightening the breech.
This had to be done 320 times to refuel all the chambers of all 5 guns in a single drift. Meanwhile, at the lowest level, the gunners would open the main breech, eject the spent casing, and set the weapon to safe. Then they loaded the new rounds with their piston and charge.
Once all of the 320 secondary chambers of 5 guns have been reloaded the gunner would get a signal that the loading was done and the refuelers had all been evacuated. Once clear the cannons would be set to fire and the firing cords would be pulled in quick succession. Then the process started all over again.
To achieve the planned fire rate this entire process should’ve taken no longer than 5 minutes and the pace would have had to have been kept 24 hours a day 7 days a week. This is completely unrealistic, especially when considering the buildup of fumes in the tunnels and any waiting for the gasses to be ventilated from the barrel. So, there is no saying what the real fire rate would’ve been, but assuming an average reload of 30 minutes for all 5 guns this would’ve given a fire rate of 1,200 rounds a day for the entire bunker.
Even with the more realistic fire rate this still involved the bunker consuming 50 rounds and 3,200 fuel cylinders every hour. Pallets of shells and fuel would’ve been constantly moved from storage and moved to the lifts using carts, from there they would have had to have been delivered to the reloading crews. Likewise, a daily train would have had to have kept the bunker stocked with fuel, shells, food, tools, and spare parts.
To maintain 24/7 operation multiple shifts of men would’ve been employed in a strict schedule. Fortunately, the plan never came to fruition due to a number of factors. While groundbreaking, the gun never achieved its promised 1500 meters per second (4926 feet per second) velocity.
Such a figure was theoretically possible, but it required far more development, for which there was no time. The Mimoyecques Fortress began construction based on the promised figures that never came. However, it had issues of its own, it was built in an area under heavy Allied scrutiny, so the construction site was bombed in November 1943, just 2 months after construction started.
The attacks forced a downscaling of the plans. The sister bunker was scrapped, and later on, it was decided to build only 3 drifts out of the planned 5, bringing the amount of London Guns set to be built from 50, to 15. However, none of it made any difference.
In July 1944 the RAF bombed it and hit the area with six 12,000-pound Tallboy earthquake bombs which severely damaged the structure and caused the collapse of the lower levels. Despite this, a V3 designed gun did see use in combat once. On December 30th, 1944 a shorter version was installed in Lampaden, Germany, and it was used to shell Luxembourg.
It fired a 207-pound version of the shell with 20 pounds of explosives. It proved ineffective. The small explosive charge did little damage, and its high penetration was unnecessary for the unarmored targets it hit.
The gun ceased firing on the 11th of January 1945 as Allied forces approached the site. Such a weapon has never been used again. As for the Mimoyecques site, it was captured by the Canadian 3rd Infantry Division in September 1944, by which time the complex was empty.
They didn’t know what the place was and neither did anyone in Allied high command. It was bombed under the belief that it had something to do with the other V-weapons, just like other sites in the region, but its true purpose would not be revealed until 1945 when the remains of the V3 project were discovered. Upon this revelation Winston Churchill ordered the bunker to be destroyed as it could have still been repaired and put into action if war ever broke out on the continent again.
On this order, Royal Engineers filled the complex with 10 tons of 500-pound aircraft bombs as well as captured German explosives. A significant amount of the explosives were focused on the drifts resulting in severe damage to the concrete slab on the surface, but most of the complex remained standing. As a result, a second demolition using 25 tons of explosives was prepared, this time focusing on the points of access.
The resulting explosion collapsed the entrances, sealing the bunker from the outside to the satisfaction of the British high command. Multi-chamber guns have never been used in combat again, however, the multi-chamber design persists outside the battlefield. The most persistent innovation from the V3 is, undoubtedly, the fin-stabilized discarding sabot round.
It is unknown how much knowledge from this and other arrow projectiles developed by the Germans made it to Allied research laboratories, but today the APFSDS design serves as the primary armor-piercing round of every main battle tank across the world. The V3 was an innovative and ambitious project with the potential to change history. Winston Churchill stated it would’ve been "the most devastating attack of all.
" Under such relentless shelling, London would’ve seen daily life and critical manufacturing grind to a halt, if the gun was used in support of an air assault it could’ve changed the outcome of the Western Front. Today the site is a museum that you can visit during the summer months. One of the tunnel entrances was reopened in 1969 by a local farmer named Marie-Madeleine Vasseur, who made the first iteration of the museum with the help of friends and family.
Today it is run by a nonprofit organization. The current museum gives access to the railway tunnel, and Galleries 9, 10, and 2, from which you can peek into the gun drifts. We visited and we'd like to thank the Mimoyeqcques museum for their help and for giving us permission to film.
Monuments have been erected inside remembering the lives of the forced laborers who died during the construction and the bombings, as well as Allied bomber crews who gave their lives attacking the site. We highly recommend a visit.
