You do understand that the guns used in WWII were for the most part rifle caliber, anywhere from 7.62mm to 12.75mm, while cannon were predominately 20mm. The reason for the smaller calibers were higher rates of fire and the ability to carry more rounds into combat. Push up the time frame 5 years and you have on the MiG-15 two sizes of gun while on the F-86 there were six .50in M2 guns. The Saber had a higher rate of fire and took out a lot of MiGs but if a MiG hit you with the slower but larger of it's guns it was lights out. The reason the US and NATO switched to 20mm cannon in their new jets was that the west built on the cannons that the Germans had developed in the 40's. The Colt MK2 was one of the first used and then GE came up with the best and fastest gun at the time the M61A2 Vulcan. Another reason guns got more lethal is the fact that you can put nastier ( read better explosives) into the rounds so you get API, APHE, AP-T and so on.
In this game, as I have said before, there was a lot and I mean a lot, of input by gents whose jobs it was and in some cases still is handling and loading aircraft ordnance. Killer Bee, ArmorDave,wpnssg and myself all had input as to how effective and realistic a weapon should be. If you think that what is used in the game is overkill, then get the editor out and make some changes but don't think you can improve on what was done. It's just a game but a real good one compared to others that you can get.