Hi NZSnowman,
To clarify
M42 LM42U single 3.7cm fitted to both type VIIs and type IXs
C38 DLM43U twin 2cm fitted both types. DLM43U would not have been able to support the 3.7cm M42 or M43
M43 LM42U single 3.7cm fitted to type VIIs and type IXs, cheaper to manufacture, greater rate of fire, shorter range (and barrel)
M42 DLM42U twin 3.7cm - U boats ]
M43 DLM42U twin 3.7cm - U boats ][size=78%] [/size][/size]same mount, just different gun[size=78%]
Or the short answer the M43 I was previously referring to was the gun not the mount. The M43 was definitely fitted to at least one U Boat, the U 534, so was most probably fitted to other boats that had their single 3.7cm upgraded to a twin during the latter months of the war, no exact date for the U 534s fitment but sometime after October '44. It would not have been necessary to develop a new mount for the M43 as its pivot point and firing linkage are virtually identical to the M42. To be honest it is very difficult to spot the difference between the M42 and M43 in wartime photos.
Regards
Jon