Reichsverteidigung

The Me 410 was also used as a bomber destroyer against the daylight bomber formations of the USAAF, upgraded with Umrüst-Bausätze factory conversion kits, all bearing a /U suffix, for the design. The A-1/U4 subtype fitted the massive, 540 kg weight Bordkanone series 50 mm BK 5 cannon, loaded with 21 rounds.

After just over three months of testing, during which various belt-feed and jamming malfunctions had been ironed out, the resulting weapon was installed in aircraft of II./ZG 26 early February 1944. Despite the fact that the weapon was still experiencing electrical problems, small switches were found to break easily and ammunition belts continued to fall apart. Also, the BK 5’s recoil and feed mechanisms were unable to cope with the g-forces of aerial combat, and it was rare for more than one shell to be fired without the weapon jamming.

Gefr. Richard Wilde:
«The Kommandeur Hptm. Günther Weyl brought us in behind the B-17s on a wide curving right-hand turn with a slight height advantage allowing for accurate firing. During our closing approach my right neighbour caught fire and peeled away with a half-roll. I managed seven or eight firing rounds with the heavy cannon with no problems. Even the smaller cannon worked well that day. I could see the impacts of my firing on the right inboard engine of the B-17 I was attacking but I took numerous hits as we closed in. I could hear the impacts and see their effects on the port wing. My radio operator Karl Lapsie reported that very hot oil was coming into his compartment, burning his legs. As I continued my attack oily smoke started to fill the cabin and when I unleashed my last cannon shell, flames erupted in the cockpit. We were right alongside the B-17's huge tail fin when I rolled the aircraft away to port, jettisoning the canopy at the same time.»