I agree with Wilbus and SageFIN. 
 I think it has got to do with damage modelling rather than 
 gun damage. A plane can be shot up real bad, but it does not
 necessarily mean structural failure.  Powerful  20mms  might
 blow large chunks off the fuselage, but it won't necessarily
 mean this damage will destroy a whole section of the   plane
 that is hit, throwing it off the flight path completely  and 
 destroying the plane due to immediate crash.
 Most of the gun-cam footage or historic photos  I have  seen  
 records fires, damaged or dead engine,occasional destruction
 of wing or blowing  up  as  the main  factor of target plane 
 being destroyed.. rather than sawing off a whole vital section
 and rendering the plane totally inoperable. 
 This sort of simplified damage model is what I think the main
 reason behind those instances of '1-ping Hispano deaths'  or
 '700 yard 4-cannon spray and pray' deaths. In these instances
 it is no doubt possible that a stray, lucky 20mm shot can hit
 and seriously damage a plane, but the damage would be more like
 a small section torn off from the vertical stabilizer or rudder,
 elevators punctured and etc. This sort of damage would put the
 enemy out of the game, but it still would probably let the 
 plane fly and hold together with the pilot inside struggling and 
 cursing. The real problem would come when the pilot tries to land 
 his plane after he escapes. Currently, in these instances, a
 Hispano cannon bird would land one or two lucky pings at the tail 
 section(in many instances these areas never even pinged before)
 and would just totally saw it off. The vertical/horizontal stabs, 
 or two elevators totally off, or a ping at the wing root totally
 knocking it off. 
 The solution lies in better damage modelling. With better damage
 modelling introduced, I predict taking a well aimed shot for
 enough time would destroy the plane. The 600~800 yard spraying
 so common with planes with guns that are able to hit up to very
 far distances would cause distruptive handling for the guy who
 is hit, but the plane would be able to limp away with speed..
 the real problem coming in the landing sequence. 
 The case of a good contending flight game IL-2 demonstrates this. 
 Shots from out of critical range do land some successful hits,
 possibly destroying parts of tail or puncturing areas of the wing. 
 But these sort of hits never ever just knock a plane outta the
 sky like hitting a pin with a bowling ball. Only when an enemy 
 plane is well within range(in AH, it would be about 50~200 yards)
 a destructive shot comes. And even in these cases the reason for
 being shot down is heavy damage to the engine, fires starting, 
 control surfaces damaged and plane inoperable.. structural failure
 like wing blown off is rare(unless it is 30~37mm guns). 
 Most common deaths I have experienced is from desperate maneuvers
 with badly damaged planes causing a stall and augering, or fuel
 leaking and catching fire. 
 And contrary to popular belief, the guns aren't undermodelled either,
 judging from my experience. It just won't go down if guns are fired
 like in AH. Quick snapshots never kill planes(they do kill the 
 pilot quite many times, however), wild shots from  200~300 meters 
 don't blow a plane, few 20mm pings don't instantly knock off a 
 wing. Only if you give it a good chase, take concentration and 
 shoot carefully will the plane go down. 
 When these sort of damage modelling is introduced in AH, I can 
 say with confidence the people complaining about Spits and N1K2s 
 would greatly diminish. The guns won't be destructive enough 
 with sphisticated damage modelling. 400~500 yard shots would rarely
 award someone a kill. The slow plane it is, planes like Spits would
 have to land a real good shot within real good range to kill 
 someone. And being able to take more damage than before, a faster
 plane would have better chance to stay alive till the seperation
 (but of course, quite badly tattered).
 And no, this is not a Luft Whining thread. The 'penalty'(if it is
 to be considered a penalty) applies the same to LW birds. Just that
 pilots who mainly used LW birds are more familiar with getting in 
 close range to fire a shot, that they won't notice that much of a
 difference. 
 Better damage modelling. The single largest request I have
 for AH and HTC.