Hitler praised the Me 410 as the “backbone of the Reich air defense” after observing a demonstration of one with a BK 5 cannon in November 1943
The Me 210 initially took to the skies in September 1939, with the intention of serving as a progressive development of the twin-engined Bf 110 Zerstorer. The Luftwaffe continued to work on the Me 210 and its replacement, the Me 410, in spite of the problems with the Bf 110. The Me 210 actually evolved into the Me 410 in late 1942 with improvements to the wings and fuselage in addition to more power.
Both planes were used as heavy fighters, fighter-bombers, platforms for reconnaissance, and interceptors. The Me 410 was equipped with a 30 mm cannon, 21 cm underwing mortars, and the massive Rheinmetall BK (Bordkanone) 5 five-centimeter cannon, which was designed to take on the USAAF’s four-engined bombers.
The Luftwaffe Technisches Amt had issued a requirement for a gun with a muzzle velocity of at least 600 m per second and a rate of fire of 300 rounds per minute. The idea was to have a weapon capable of inflicting almost certain damage on enemy bombers, but without the attacking aircraft coming within range of the enemy’s defensive fire. This is according to Robert Forsyth in his book Me 210/410 Zerstorer Units.
The paradox was that even though accuracy and extremely low dispersion were necessary, it would be unable to fire at a high rate of fire due to the heavy-caliber ammunition needed. Every shot had to be significant. The Me 410 and Ju 88 were the two aircraft chosen to test this weapon.
Officers on the staff of the General der Jagdflieger first suggested using a five-centimeter cannon in the Me 410 to E.Kdo 25 in July 1943. They envisioned using a five-centimeter KwK (Kampficagenkanone) 39 tank gun, which belonged to the Wehrmacht. It was believed that a bomber might be brought down with just one five-centimeter strike using the Revi 12C/D or Zielfernrohr ZFR 4A telescopic sight. However, the ZFR 4A needed a lot of practice, gunnery expertise, and the ability to maintain a stable firing position for an extended period of time in order to be used effectively.
The alterations required to fit the big gun into an aircraft such as the Me 410 were thought acceptable, given that this would avoid the development of a new weapon. The cannon would become fully automatic if a magazine was added, and it could be constructed as a single unit with the gun, mounting, and magazine-feed system for simple interchangeability. Electro-pneumatic loaders were used for loading, and an electric primer was used to fire the ammo. Two hydro-pneumatic cylinders positioned above the gun cradle served as the recoil absorbers.
The bomb-bay doors were removed and a ventral fairing was used in place of them on the Me 410 to secure the back portion of the gun to the main spar. The installation of the gun turned out to be so successful that the ventral fairing’s outline only required to be expanded from the original design by around 100 mm at its deepest point. The rear of the panel had a cartridge ejection aperture with an internally mounted chute.
A perforated muzzle brake allowed the muzzle blast to be evenly spread over the airframe, preventing any damage and avoiding the need for reinforcement. The only issue was that it was difficult to keep the gun heated at altitude, therefore heating came from the crew compartment.
A Steinbock, a sizable transportable hydraulic jack, was used to raise the gun into a Me 410. A rope was used to secure the muzzle end of the barrel to the Steinbock arm, which was then pumped up until the mounting’s back was tilted upward. The gun and Steinbock were then brought in from underneath the fuselage and lifted until the clamp of the setting mechanism lined up with the plate attached to the main spar. After that, two locking bolts were screwed in. The mounting of the gun was held in place with the aid of a gimbal ring, a pair of lateral bracing tubes, and a suspension stirrup.
It appears that by the end of October 1943, Galland’s office had changed its mind about the BK 5 and now thought that a rapid-fire weapon like the MK 103 would be preferable. Hitler said that the Me 410A-1 was the “backbone of the home air defense” after seeing a demonstration of one with a BK 5 cannon in November. The Me 410 must be dedicated to Reich defense, and two Gruppen or a Geschwader must be outfitted with the aircraft and weaponry, according to the Fuhrer.
Given the lack of additional cannons, Goring had the guts to tell Hitler that only two or three aircraft could be fitted with the BK 5. Considering that the majority of Me 410s had been assigned to bomber Gruppen for missions over England, the Reichsmarschall gave Generalfeldmarschall Mitch the go-ahead to begin outfitting two Gruppen with 45 cannon-equipped aircraft each on January 12, 1944. Two days later, in response, Milch wrote to Goring;
`The first experimental aircraft have been equipped with a 50 mm gun. Since this gun can no longer be delivered, a conversion for a new 50 mm gun had to be carried out within a very short period of time. This new gun is installed in a different manner. The first delivery of ten guns was to be made in December. This was not possible since the magazine feeding device which we constructed suffered stoppages due to broken belt links, whereby the cartridge was hitched to the belt conveyor table. These defects have now been eliminated. There have been difficulties experienced with the high-explosive shell we developed on account of casting defects in the casings and also with respect to its dispersion because of the rotating bands. Alterations are being carried out in the plants. The results have still to be tested.’
Following the original investigation at Tarnewitz into the BK 5-equipped Me 410 V2, Deutsche Lufthansa at Berlin-Staaken began work on adapting the gun for aerial usage. The finished weapon was mounted on aircraft of II./ZG 26 as the Me 410A-1/U4 beginning in early February 1944 after just over three months of testing, during which time significant belt-feed and jamming malfunctions had been resolved.
In order to resupply, the Gruppe relocated from Hildesheim to Oberpfaffenhofen, and by February 8th, Staffel 5 had 12 cannon-equipped aircraft. Despite the fact that the weapon was still having electrical issues, minor switches were discovered to be easily breakable, and ammunition belts continued to fall apart, trial operations were promptly launched over southern Germany and Austria. Additionally, the BK 5’s feed and recoil mechanisms were not designed to withstand the G-forces of airborne combat, and it was uncommon to fire more than one shell without the weapon jamming. The addition of an improvised cleaning device helped to some degree to address these problems.
However, in most cases, Goring and the high command’s insistence that the units use large-caliber guns turned out to be a mistake. Instead of developing guided rockets, it would have been preferable to employ unguided rockets.
When the daylight war over the Reich reached its peak in October 1943, the USAAF was forced to accept that unescorted, deep penetration formations could not provide sufficient self-defense. Although these missions resulted in unacceptable levels of loss, they still compelled the Luftwaffe to engage in aerial combat, causing attrition to a degree from which the Germans would find it challenging to recover.
On October 10, the Kommodore of ZG 26, Major Karl Boehm-Tettelbach, led his Bf 110s, together with Me 410s of III./ZG 1 from Hesepe and Osnabruck, in an attack on the marshaling yards at Munster against B-17s of the 3rd Bomb Division. The 14th Bombardment Wing was particularly hard damaged by the Zerstorer in a mass attack from the rear near Munster, after the 3rd’s B-17s, which had been abandoned without any escort owing to bad weather over England, had already been mauled by single-engined fighters. In fact, the Bf 110s of ZG 26 claimed to have destroyed 14 B-17s, making it their single most successful day. On the other hand, and somewhat surprisingly, the Me 410s of III./ZG 1 did not return with any laurel.
Early October sorties by I./KG 51 also had little success. In a return to the aircraft industry targets that had proven to be so costly to the USAAF in August, 229 of the 291 B-17s that were dispatched managed to reach Schweinfurt on the 14th. The Me 410s of I./KG 51 took off from Horsching under Jagdfliegerfuhrer Ostmark and flew west until they established visual contact close to Schweinfurt, where the bombers had already dropped their ordnance on the city’s ball-bearing plant.
The Messerschmitt aircraft pursued the bombers into the enemy formation while following them and firing their mortars. Once more, the highly efficient defensive fire of the bombers trapped the Me 410s, and while the Gruppe was lucky to escape without damage, it made no claims. Prior to being deployed for missions over England, it turned out to be the unit’s final such mission.
Me 210/410 Zerstorer Units is published by Osprey Publishing and is available to order here.
Photo by U.S. Air Force, The PIPE and Mike Freer via Wikipedia