Originally posted by scJazz
Tony your point about 3 MK108s weighing as much as 6 .50s is noted. However in almost no cases were highly produced aircraft fitted with 3 MK108s.
I know, I was comparing the guns rather than specific aircraft fits. The only single-engined fighters I can think of offhand which had three MK 108 were some of the last anti-bomber Bf 109s (they also had a pair of MG 131's of course).
For less weight and probably even less volume the ME 262 could have been fitted with 12 MG 131s. In a nose mounted arrangement with no convergence problems this would have been devestating! Longer ranged and faster slugs would have made the odds of actually landing a hit extremely probable. Roughly 6 MG151s could have also been used and this would have worked out almost as well. Considering LW design concepts it would have been the most likely choice besides the MG131. However I don't think it would have been as effective.
The German experience was that large numbers of small shells were not as effective as one big shell of the same weight; what usually mattered in bringing down an aircraft was the concentration of damage at one point, rather than scattering lots of hits all over the aircraft.
Of course, the Germans became obsessive about knocking down heavy bombers, and their armament was increasingly biased towards this. As you say, for the same weight as four MK 108 they could have had six MG 151s, which would have been much better against fighters because of the higher hit probability, couple with the fact that 20mm shells were generally powerful enough to do the job. I don't think that a battery of MG 131s would have been as good; the ballistics were worse, the little shells contained very little HE and the AP versions didn't have much penetration either.
Tony Williams: Military gun and ammunition
website and Discussion
forum