Hi Wolfala,
>I believe the .50 debate is 2 fold: Supply chain, as pointed out earlier. The other reason is the lack of need for buff busting. The allies weren't faced with heavy armada's of bombers which required cannon to crack. And since the AXIS never developed anything along the lines of the B-17 or B-29, or fielded them in any threatening numbers - maybe it was a moot point.
Let me point out what I consider the two vital flaws in those points:
1) Supply chain.
Switching the fighter squadrons over to cannon entirely would not even have increased the number of spare parts as you could drop the 12.7 mm MGs from the supply chain. If the bombers would have kept it, fine, but they had thousands (or ten-thousands ...) of type-specific spare parts in their supply chain anyway.
Besides, in logistics, the high-turnover, low-value articles that are continuously directed to a high number of recipients - like cannon and ammunition - are not a problem at all. What you are worried about are high-value, low-turnover parts, especially when they are mission-critical, such as radar sets for lead bombers or jamming equipment for electronic warfare.
(The Luftwaffe routinely used up to three different types of guns with non-interchangable ammunition on a single aircraft type, and I never read anything about supply difficulties until the breakdown of the transportation system in the last weeks of the war made fulfilling even the simplest demands highly difficult.)
If the US Army had been free of bias and illusions, they would have asked themselves: "Do we want to accept a weight penalty of 684 lbs in the P-47 to make the life of our bean counters a tiny little bit easier, or do we switch to cannon armament?"
2) Cannon were only necessary to combat bombers.
The German military had cannon developed as universal air combat weapons, recognizing early that MG armament would be insufficient, with their combat experience (which included a lot of MG use due to the delay in employing technology) confirming the inadequacy of machine guns. They also conducted ballistic research to find the best way to destroy stressed-skin all-metal aircraft, and arrived at the high-explosive mine shell.
What's more, the Luftwaffe fielded a 15 mm cannon that the USAAF later attempted to introduce as a replacement for the 12.7 mm HMG, and quickly and universally upgraded it to 20 mm because the weapon was much more effective firing medium-velocity cannon shells than it had been firing high-velocity projectiles of with only a light explosive or incendiary warhead.
In the development of cannon as air-to-air weapons, there was no connection to the bombing offensive against Germany at all - even the MK108 had been introduced into service before the Schweinfurt raid for the first time convinced the German leadership that bombers were indeed going to be a serious threat.
Two cannon simply were a better way of delivering the same firepower as eight heavy machine guns, regardless of the type of the aircraft they were used against.
Again, there is hardly an simpler way of improving the P-47 performance than removing 684 lbs of excess weight by changing it to a more modern armament battery. If the USAAF had realized this (they didn't even come close), better supervision of the build-up of Hispano production in the US would have made the replacement of the Browning MGs with cannon a realistic possiblity.
With regard to the impact of weight, if you look at his article on the F8F, you will see that Grumman went to incredible lengths to save just 230 lbs. (They deliberately weakened the wing to an ultimate load of just 7.5 G and allowed the wing tips to separate in a safe and controlled manner if these 7.5 Gs were exceeded.)
http://www.findarticles.com/p/articles/mi_qa3897/is_199808/ai_n8826530Regards,
Henning (HoHun)
