During TT myself, squat2, bunnies(Ardy123) and Agent360 had ongoing issues with the K4's 30mm not killing planes from point blank. I flew behind a P51B inside of 200d and held the trigger down point blank for all 65 rounds. One of the last 3 30mm took his wing off. Before that I saw repeated 30mm flashes but no damage. Each of the mentioned players experienced the same phenominon. Close range hits, 30mm explosion, no damage.
This could be internet or the furball we were in effecting things with lag. We each independently made the same observations on range channel because of how unusual it was to hit planes point blank and see the explosion but nothing happen. 20mm and 50cals worked as expected in the same furballs.
Hope this is just a localised one night thing.