One of the most interesting weapons of World War II was the V-3, the little-known third Nazi “vengeance weapon.” It was an ultra-long-range cannon that used multiple breeches or powder-chambers, fired in order as a projectile shot down the barrel, right as it passed each chamber, to overcome the limits of standard artillery. It fired a subcaliber “arrow-shot” (Pfeilgeschuss) and was expected to hit London, accurately, from mainland France.
A site at Mimoyecques, France was the main location for the V-3. Over fifty tubes were planned for this weapon at this site, but the site was destroyed by bombardment by the RAF, using gigantic Tallboy bombs. As a result, the V-3, the “London Gun,” never fired a shot at England.
A German-language web page on the V-3 site at Hermes-Lampaden adds to our knowledge of this odd weapon’s history, because the Hermes-Lampaden V3s were fired in anger, at the allied-held city of Luxembourg. The website provides us with a launch pad to look at this weird weapon.
In 1942 engineer August Coenders, Chief Engineer of the Röchling firm, began to research the idea of the multi-chamber cannon, an idea in existence since the 19th Century. With the multi-chamber cannon principle, side-mounted propulsion-charge chambers were added to a cannon barrel, chambers whose propulsion charges were detonated after the projectile had passed them by, and which therefore brought higher velocities.
Coenders developed a multi-chamber cannon in 1942 under the cover name “High Pressure Pump. Soldiers nicknamed it, due to its unusual form for a cannon, “Tausendfüssler” meaning “Millipede,” or “Fleißiges Lieschen”, meaning, approximately, “Busy Lizzie.” The Nazis named it, in their taxonomy, V3, for the third operational “Vengeance Weapon.” The maker of the barrel sections for the piece was the firm Röchling Steel Works in Völklingen, Saarland, with finishing (final machining?) at Wetzlar. The arrow-shaped, two meter long projectiles (150 mm caliber) which were designated “Rö Be 42” were also developed by Röchling.
Coenders developed versions of his very long, fin-stabilized sub-caliber shell for conventional artillery also — his big idea was to increase penetration by increasing sectional density, and it can be argued that his research led, after the war, to the common APFSDS (Armor Piercing Fin Stabilized Discarding Sabot) round that tanks these days fire at enemy tanks.
The V-3 version of the Coenders round weighed 40 kilograms, of which 7-9 were explosive. It was 100mm with fixed tail fins and used front sabots and a rear sabot/obturator to fit in the HDP’s 150mm bore. The round left the muzzle at about 1050 meters/sec (3445 fps), almost instantly shedding its sabots, at least according to the drawings. Other sources suggest that the round barely broke 3,000 fps in combat applications).
The Mimoyecques installation was destroyed by the RAF’s legendary 617 Squadron in July, 1944, and then soon afterwards overrun. But as the site explains (in the German; translation is ours with notes [in brackets], or you can try the goog thing):
After the Allies captured the Channel coast near Mimoyecques in September 1944, the plan to bombard London with up to 50 HDPs from the bunkers had to be abandoned. SS-Gruppenführer [~Colonel] [Hans] Kammler, to who the Vengeance Weapons detachments were subordinate, wanted to prove the combat suitability of the V3 beyond question, and sought from Hitler the permission to employ the HDP against the City of Luxembourg during the Ardennes Offensive [Battle of the Bulge].
To this end two shortened versions of the HDP with the designation LRK 15 F 58 (Langrohrkanone) [Long Barrel Cannon] were emplaced in Ruwertal near Hermeskeil-Lampaden. They were put into action by the Firts Battery of the Army Artillery Detachment 705. [This unit was an independent artillery unit that was under the command of the Kammler-controlled Vengeance Division (Division zur Vergeltung)]. The emplacement of the first gun took from 28 Nov 44 to 23 Dec 44, the second needed a little more time. Two steel guns were erected, which were positioned on a wooden substructure. The wooden substructure was half buried in the slope. The barrel elevation was 34°. This shortened version of the High Pressure Pump was no more than 50 m long and was fitted out with 12 side chambers attached at right angles. The cannons had a range of up to 60 km with a dispersion of up to 4 km.
That’s a pretty large group; an online angular size calculator tells us it’s 3.8 degrees, or 229 minutes of arc/angle. We suppose that if your target is, as was the norm for V-weapons, “minute of major metropolitan area,” that accuracy was acceptable.
The Mimoyecques guns had been meant to be 150m long and range 165km; the whole battery was supposed to be capable of firing 300 shells an hour on London. One gun intended for Mimoyecques provided some parts for both Hermeskeil-Lampaden guns, except that the Mimoyecques guns had the auxiliary chambers aligned in herringbone fashion, and the H-L guns had them set orthogonal to the gun’s bore.
The H-L guns, illustrated in this 26 Nov 44 drawing, were set at 34º and were made up of 13 straight sections and 12 cross-sections (where the chambers attached), and they hoped to deliver 3-4 shots per hour.
The V3 bombardment of Luxembourg was irritating and frightening, but of no military consequence. The pair of V-3s fired a total of 183 rounds, of which only 44 were confirmed as hits in the target area. It’s uncertain whether it was the rounds on target, or the 139 that landed somewhere off target, that killed 10 people and wounded 25 — a pretty pathetic result. The guns were dismantled in February 1945 when the Germans withdrew from the area; the second gun was not taken out of action until the US Army was closing in. In 1945, parts of four HDPs were found at the Röchling plant, and removed to the USA for testing. They were subsequently scrapped.
Here are some links in English on the V3: