Hi Krazykraut,
>Now confusingly, the only drawing I have found shows a much smaller and much more streamlined blister for these guns than the Gustav later would get. Anyone know why this much more aerodynamically looking version was not adopted for wider use?
I've just seen a post on another forum that pointed out that the "standard" bulge accomodated the chute to the container for spent cartridges.
The drawing you posted shows that the spent cartridges are not collected, but ejected from Galland's converted aircraft.
I'm not sure what the reason might be - perhaps the ejected cartridges were feared to inflict damage to the tail of the aircraft?
(I don't know if a larger, but sealed blister might actually cause less drag than a smaller blister with an opening. Cowl aerodynamics could be complicated at times.)
Regards,
Henning (HoHun)