Few commentators seem to be in any doubt but that the V-3 was the “High Pressure Pump” or “England Gun”. Paul Brickhill recorded in The Dam Busters:
“the greatest nightmare of all was the great underworld being burrowed under a 20-foot-thick slab of ferro-concrete near Mimoyecques (between Calais and Boulogne). Here Hitler was preparing his V-3. Little has been told about the V-3, probably because we never found out much about it. The V-3 was the most secret and sinister of all – long-range guns with barrels 500 feet long!”
The V-3 was probably based on the 1885 unsuccessful ballistic principle of the Americans Lymann and Haskell and Baron von Pirquet’s concept of sequential, electrically activated, angled side chambers to provide additional velocity to a shell during its passage of an immensely long tube.
In mid-1942 August Cönders, chief engineer of the Röchling Iron and Steel Works, Leipzig, rediscovered the principle while reading through technical dossiers captured by the Germans in France in 1940. He worked out an improved design and approached Armaments Minister Speer with the idea. Hitler was enthusiastic and demanded that the development should proceed immediately.
The design was for a gun consisting of numerous lengths of smoothbore metal tubing bolted together to form a barrel up to 124 metres long. Every 3.65 metres along its length was a lateral combustion chamber set at from 45° to a right angle. The shell and main propellant were loaded into an sFH18 heavy field howitzer breech. When the gun was fired, the projectile would be impelled forward by pressure from a gas cartridge, and on passing each chamber it triggered electrically another cartridge positioned there which gave the shell further velocity. This was repeated throughout its transit of the barrel. The electrical activation solved a detonation problem which had been caused by expanding gases detonating the auxiliary chambers before the arrival of the shell. The muzzle velocity was around 1500 metres/sec which was significantly greater than that of standard artillery and provided a range of about 160 kilometres. The original 10-inch calibre projectile was over nine feet in length and weighed 140 kilos with a 25-kilo warhead. Six wings opened in flight for stability. Twenty-five guns were projected which at full output would have enabled London, 150 kilometres distant, to be subjected to a persistent rain of up to 200 ten-inch calibre shells per hour. For this reason the project was nicknamed fleissiges Lieschen, Busy Lizzie. The Heereswaffenamt, or German Army Weapons Office, contracted with firms such as Skoda, Krupp, Röchling, Witkowitz Iron and Steel, Faserstoff, Fürstenberg and Bochumer Verein for various calibres of ammunition. Towards mid-1944 20,000 shells were completed or under production.
Even before the gun trials had begun, work was started in the late summer of 1943 on a vast, well camouflaged underground gun battery to house twenty-five barrels of the HPP on the Channel coast at Mimoyecques. The barrels were to be sunk in shafts at a 50° angle 150 feet down into the ground. A slave labour force of 10,000 persons was involved in the construction and information was soon passed to London about a new mammoth “underground V-1 site”.
The initial tests were carried out using barrel lengths between 50 and 130 metres, first at Hillersleben and then from a range at Misdroy near Peenemünde at the beginning of 1944. Various permutations of barrels and chambers were tried without much success. Shells were supplied by numerous manufacturers. In tests between 21 and 23 March 1944 it was found that at muzzle velocities above 1100 metres/sec the tubes lost stability and developed metal stresses. General Leeb recommended that the project be stopped for investigations. By May 1944 the gun had an acceptable range of 95 kilometres and experiments were stepped up to find ways of increasing muzzle velocity. Before any guns were delivered, the Mimoyecques emplacement was destroyed on 6 July 1944 by RAF aircraft using a 12,000-pound Tallboy bomb. This signalled the end of the project for the long-range bombardment of London and put the entire V-3 project in question.
Nevertheless further trials with the HPP with shorter barrels were undertaken at Misdroy and eventually the whole project was placed in the hands of SS-Obergruppenführer Hans Kammler, head of the V-weapons project. Under his supervision the V-3 project was accelerated for an operation in the late autumn of 1944 and, with the help of General Dr (Ing) Erich Dornberger, military commander at Peenemünde, a battery of two 50-metre long 15-cm (5.9-inch) calibre barrels with twelve right-angled side chambers was completed. An emplacement had been excavated at Bürderheidermühle on a wooded slope of the Ruwer at Lampaden, about 13 kilometres south-east of Trier, where the battery was installed under the supervision of Hauptmann Patzig and his 550-strong Army Artillery Detachment 705.
The two HPP barrels rested on thirteen steel girders anchored to buried wooden foundations and were laid to the west with a 34° elevation. 43 kilometres along the firing line was target number 305, Luxemburg City. Calculations showed that the two guns had a maximum range of 65 kilometres with a shell dispersion radius of from 2.5 to 5 kilometres.
Between the two barrels were three bunkers for the gun crews plus either side of the barrels ten smaller bunkers which served as shell and powder magazines.
The Lampaden emplacement was part of the plan for the Ardennes offensive. Ammunition supply was poor because of disruption to the railways and in view of the critical time factor it was decided to use a 95-kilo shell of 15-cm calibre with a warhead of 7 to 9 kilos. The propellant was a 5-kilo main cartridge and twenty-four additional chamber charges, a total of 73 kilos of Ammon powder per shell.
Neither gun was operational when the Ardennes offensive began on 16 December 1944. Hurried preparations were being made to support the German offensive from Lampaden. Luxemburg City, liberated by the Americans in September 1944, was finally chosen as the target for diversionary fire. Although the battery was only operational to a limited extent on 20 December, Kammler was told by High Command West to have it ready before New Year.
On Saturday 30 December 1944 No 1 Gun opened fire. The flight of shell from Lampaden to Luxemburg was 42.5 kilometres. Because of muzzle velocity variables and the variety of propellants being used it was estimated that the target zone was from 40.6 to 43.6 kilometres, giving a dispersal of salvoes of about 3 kilometres. The exact barrel elevation was set at 36° and the muzzle velocity 935 metres/second.
Two ‘warmers’ were fired at 2145 hrs and 2205 hrs before Oberleutnant Bortscheller ordered the gun to open fire in earnest at 2216 hrs in the presence of SS-Obergruppenführer Kammler, the battery commander and officers from a neighbouring artillery detachment. Fire ceased at 2343 hrs. Five shells exploded more or less in the city centre but what effect they had is unknown.
According to German sources, these were 95-kilo shells, probably the six-winged Röchling type numbered 32, 29, 47, 15, 28 (firing sequence). On 31 December twenty-three more were fired between 0007 hrs and 2333 hrs from No 1 Gun, while No 2 Gun was still being adjusted, this not being completed until 3 January.
Following round 17 fired at 0944 hrs the pressure tube was found to have shifted by 4 millimetres and had to be realigned. After two ‘warmers’ the remaining shells were fired without incident between 1943 and 1958 hrs.
4 January 1601–2007 hrs. No 1 Gun, 16 rounds. No 2 Gun ready but did not fire.
11 January 2016–2351 hrs. Both guns fired, total 20 rounds.
12 January 1847–2224 hrs. Both guns fired, total 20 rounds.
13 January 0757–1238 hrs. Both guns fired, total 22 rounds, after which both barrels were checked and adjusted. Because of ammunition shortage, fire was not resumed until 15 January.
15 January Early afternoon, six shells exploded in Luxemburg City.
16 January Late afternoon, six rounds fired. The tower of the cathedral was hit and four persons attending mass were killed.
18 January 1421–1638 hrs. Both guns fired 19 rounds. Most of these exploded north-east of the city in the suburbs of Clausen, Neudorf and Hamm injuring 13 persons.
20 January 0808–1353 hrs. Both guns fired a total of 24 rounds.
Preparations had been taken in hand to transport and mount two more barrels with selected lines of fire into Belgium and France and existing HPP ammunition was rationed out between the four guns. By now the Americans were counter-attacking successfully in the Ardennes region and as it was obvious that Lampaden would soon be under threat, Kammler ordered the detachment to be prepared to dismantle the two pressure tubes for a withdrawal east of the Rhine in due course. The lack of ammunition remained severe.
15 February 0908–1735 hrs. No 1 Gun fired 20 rounds at Luxemburg. These all fell in unpopulated areas near Hamm and Sandweiler east of the city.
16 February 1020–1405 hrs. No 1 Gun fired four shells which fell near Fetschenhaff causing little damage. According to German sources the battery had now only six rounds left.
22 February 1745–1858 hrs. Six shells were fired, all off-target and landed in open country near Merl. This terminated the V-3 programme and the guns were dismantled for transport across the Rhine.
On 26 February US armoured units advanced to within 3 kilometres of Lampaden where they captured guns and replacement parts. A quantity of ammunition was also confiscated and tested later at the Aberdeen Proving Ground, Maryland. The V-3 HPP was considered to have limited value and needed further development. Operationally 183 rounds had been fired from Lampaden towards Luxemburg of which 143 (78%) exploded within the territory or very close to it.
The V-3 suffered from lack of development due to the pressure of time. Had the Mimoyecques battery been operational against London in 1943, delivering 200 6-inch shells per hour, Paul Brickhill’s fears might easily have been justified.