109F-2: MG151 upgrade 15mm --> 20mm
 

This topic is a bit unclear to me, until today I only knew that upgrading did happen in 1941. But it was not clear exactly when and to which extent.

In a Hermann-Graf-bio, today I read that his whole Staffel 9./JG52 got that upgrade on 14th of October 1941.

Does anyone else have more info on this?

Plus/minus, the autumn of 1941 can be taken as an upgrade date for all units, I think. Maybe Western Front a bit earlier...