This is what I found on
Wikipedia.
The He 111H-1 was fitted with a standard set of three
7.92 mm (.312 in) MG 15s and eight SC 250 250 kg (550 lb) or 32 SC 50 50 kg (110 lb) bombs. The same armament was used in the H-2 which started production in August 1939.
[45] The P-series was gradually replaced on the eve of war with the new the H-2, powered by improved Jumo 211 A-3 engines of 820 kW (1,100 hp).
[45] A count on 2 September 1939 revealed that the
Luftwaffe had a total of 787 He 111s in service, with 705 combat ready, including 400 H-1 and H-2s that had been produced in a mere four months.
[46] Production of the H-3, powered by the 895 kW (1,200 hp) Jumo 211 D-1, began in October 1939. The experiences during the Polish Campaign lead to an increase in defensive armament. MG 17s were fitted whenever possible and the number of machine guns was increased to seven. Normally one MG 17 would be installed in the nose, one in the ventral position, dorsal position and one in each waist window position. The two waist positions received an additional MG 15 or 17. On some Heinkels a permanent
belt-fed MG 17 was installed in the tail.
[45]