Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
The difference between AA work and aircraft work is that the air to air combat uses much less firing time. Keeping an enemy plane in the gun sight for more than 3 seconds was rather rare. AA gunners tended to hose the sky as the aircraft approached. Few guns exceeded their ammo supply in 3-4 seconds but many 20mm guns with 60 round drums could run dry in 6-8 seconds.
From Navweaps on the .50 cal, "Shipboard gunners of the 1930s-40s using water-cooled versions were trained to fire continuously in order to be able to "walk" the tracers onto the target. As the practical range against aircraft for this weapon was approximately 1,500 yards (1,400 m), an aircraft approaching at 200 knots would be under fire for about 14 seconds, or the rough equivalent of one belt of 100 rounds."
Some Axis guns (German, Japanese, Italian) used smaller magazines for their automatic AA guns, 12 to 30 rounds depending on type and caliber so the 'practical' rate of fire becomes much more important. But this is for AA work.
For the belt-fed aircraft weapons, the cyclical RoF is the only one that matter.
Few guns exceeded their ammo supply in 3-4 seconds but many 20mm guns with 60 round drums could run dry in 6-8 seconds.
And of course the low muzzle velocity is not a good thing, I've heard they were difficult score hits with at range.
At 575 m/s of muzzle velocity, the trajectory was pretty curved for any distances bar the really short ones. Would take a real master (or a computing gun sight, like the K-14 used by the Allies at the last year of the ww2) to land hits on a small, fighter-sized A/C that is at some distance.
This compares to the F4F Wildcat that had about 22-23 seconds of firing time on target.
The difference in ballistics between the various guns ( of any nation) doesn't matter that much at close ranges. Usually 300yds or under and is a bigger problem with deflection shooting than firing from 6 O'clock or near to it.
...
As an example using German guns (mostly because that is what I can find the figures for)
...
20mm HEI 92 gr........695...............432...................0.551........................281.....................1.428 (1)
20mm HET 117gr.......720..............552....................0.447.......................422.....................1.101 (2)
...
Notes:
1, fired from MG-FFM
2, fired from MG 151/20 (change in nose shape and higher weight)
3, Ausf. A fired from MK 108
4, Ausf, C fired from MK 108 (notice change just due to nose shape)
From Tony Williams and Emmanual Gustin's book "Flying guns of World War II"
Please note that it is quite possible for the German 20mm projectiles even when fired from the same gun to arrive at rather different times at ranges around 600 meters.
...
Yeah, understand about ballistics not being an issue at close ranges. Problem I see at any decent range -..........
And the firepower of 2 7.7 MG's is almost negligible.
The 92 gram 20mm shell would be the Mine shell, the 115 gram is the 'usual' one?
Well, that "negligible firepower" accounted for a fair number of allied aircraft from Dec 1941 to the summer of 1942. A large number of the KI 43s having only two 7.7s. Problems with the 12.7mm Ho-103 (or ammo supply ?) means a lot fewer Ki 43s had one gun of each caliber than was commonly thought.
Define "decent range" please? Germans figured the "effective" range against 4 engine bombers for the majority of their aircraft guns as 400 meters (leaving out the 15mm MG 151, 30mm MK 103 and the 5cm BK 5).
Please note that if firing shells that have even a 0.2 second difference in time of flight against a 200mph bomber (300fps) from the 3 or 9 o'clock position the impact points will be 60 ft apart. And since the heavier (115-117g) shells are the ones with tracer elements that means the mine shells mixed in the belt land where if the pilot is using tracers to correct fire?