My theory about why the Luftwaffe moved away from the 5-gun configuration is simple ... the pilots didn't think it was any better than the 3-gun or didn't like it as much. Simple!
OK, but
WHY?
More firepower with no loss of performance (or minimal), what's not to like?
Or is there a loss in performance or
feel of the aircraft? Something that makes the pilot/s dislike the the 5 gun set-up?
IS it one thing or a combination of a lot of little changes in the way the airplane flies?
As I said in an earlier post there has been a division of opinion on this issue among us later day non-flyers for years with the Pro German ( or more correctly Pro 5 gun 109 fans) claiming there was little difference between the two planes and the other side claiming there is.
You have done a lot of reading,
why did some of the German pilots dislike the 5 gun set up? Is it true that the Germans tended to equip squadrons (or units) with either one option or the other ( no formation flying with different gun set ups)? Were the different gun set ups used for different missions? I fully under stand that the 3 gun fighters could wind up intercepting bombers and 5 gun fighters could end up fighting allied escorts,
The best plans only last until contact with the enemy is made. But what was the intention of the Lufftwaffe? And if there was a different "mission" intended for the 3 gun and 5 gun,
WHY?
My own opinion is that the addition of the under wing guns did degrade flight performance and in a number of areas. It may have made very minor changes in certain aspects and gone to minor or not so minor in other areas. The loss of level speed is not that great and is less than the variation between a good airframe/engine and an airframe/engine that just scrapes though the acceptance test. I don't see why there should be ANY difference in peak or max roll rates. I do think there may be a small difference in the amount of time it takes to get to a high rate of roll but again, comparing just two planes may not provide a definitive judgement. The British certainly seem to have had a problem with aileron response varying from supposedly identical Spitfire to another even without the differences in wing tips and aileron construction. It may be this greater 'inertia' that helped change the "feel" of the plane even if the rate of roll didn't change, maybe not.
The Change in rate of climb is going to change the performance of the the airplane. as an illustration see:
http://www.zenoswarbirdvideos.com/Images/P-51/P-51NPC.gif
at the increased weight and power settings in the example the rate of climb of the heavier airplane is about 80% of the "same" plane using the same power levels. The problem comes at the higher altitudes where the
SAME 300-350fps loss of climb becomes a bigger percentage of the total climb rate. I would also note, in the example given (and the difference for a 5gun and 3 gun 109 could very well be less) that even at this "cruise" climb after 18 minutes the heavier plane will be a couple of miles behind and 5,000ft lower. Certainly the "leader" can throttle back but that doesn't help the intercept problem does it?
as for the turning aspect. see:
http://www.spitfireperformance.com/spit109turn.gif
Find the curved line marked "angle of straight climb" going across the chart. At any combination of speed of "G" below the line the plane can climb. the further below the line the faster it can climb. At any combination of speed and "G" above the line the plane MUST descend to hold speed. the higher above the line the more the plane must descend to hold speed or it can hold altitude ( for a while) and bleed off speed. At any point along the line the plane can hold the speed and the rate of turn "G". changing the rate of climb moves this line up or down the chart. Adding a couple of hundred Kg to the plane may not change the "G"s that much or even the radius by much ( a few percent?) but moving that line up or down the chart ( or one drawn for 8000 meters) by by 15-25% (depending on altitude) IS going to change the the way the plane feels to the pilot. Where the lighter plane might be climbing at 250mph and a 2 g turn (60^ bank) the heavier plane might struggle to hold altitude or even slow down or descend slightly in the same maneuver.
It is my opinion that this loss of climb and "turn performance" is what the pilots didn't like, and it would be more pronounced at 7-10,000 meters than down lower.