Historical torpedo fusing

[andqui]

I'm finding lots of contradictory information about this. What types of detonators were available for different torpedoes at different times.

For example, this is what I have been able to find:
G7a T1: Impact and magnetic (both reliable)
G7e T2: Impact and magnetic (magnetic very unreliable, after Norway impact only shots ordered. Impact also somewhat unreliable)
G7e T3: Impact and magnetic (both reliable, all torpedos after this feature reliable detonators)

Is this information accurate. One source said that the G7a only had contact detonators. If they also had magnetic, were they of the same type as the T2 (i.e. very unreliable?) Was the G7a's contact detonator also unreliable, or did it and the T2 use different versions?

Last, does GWX or any other mod accurately simulate the failure rates- I ask because I'm playing in late 1939 and early 1940 at the moment and have noticed no duds or prematures or other failures.

thanks