[Juha]

Nothing exact but a bit of general info on the subject.
From my homepages:
"The Battle of Britain by Richard Hough’s and Denis Richards (Coronet edition 1990 ISBN 0 340 53470 2) p. 156 note** refers the results of a study based on opinions given in 1988 by some 100 surviving Battle of Britain era British fighter pilots. 40 of them rated the quality of German bomber gunnery good or excellent, 32 thought it average and 30 poor. In the text there is a short description of the combat on 13 August 1940 between the tight formations of the Dornier Do 17Zs from the II. and the III./KG 2 and the Spitfires from the 74 Squadron and the Hurricanes from the 111 and the 151 Squadrons during which the air gunners shot down two British fighters, but the KG 2 lost five Dorniers and four more badly damaged. In the note there is also mentioned a combat during which 9 He 111s shot down three out of the first six attacking Hurricanes. This probably refers to the combat between 9./KG 55 and 79 Squadron over the Irish Sea on 29 September 1940. 9. Staffel lost one He 111 and two others were so badly damaged that they were forced to turn back (out of 9 He 111s) but He 111 gunners shot down three Hurricanes out of 11."

Ps. The text is 13 years old.