By late 1942 reports were coming in about the ineffectiveness of the MK 101 against newer versions of the Soviet T-34 tanks. One obvious solution would be to use the larger BK 3,7 ("Bordkanone" 3,7), recently adapted from the ground-based 3.7 cm Flak 18. These guns had already been converted into underwing pod-mounted weapons for the Junkers Ju 87G and found to be an effective weapon, despite the fact that only 12 shells per pod could be accommodated. When mounted on the Hs 129, the empty area behind the cockpit could be used for ammunition storage, greatly increasing the supply compared to the Ju. The B-2/R3 package introduced the BK 3,7 automatic cannon, but relatively few aircraft were converted in favour of the B-3, mounting the BK 7,5.