Ok here's my take on it. I don't see the fight as a failure - you did enough to avoid getting killed and got the 51 on the defensive several times. You're right in saying if it was a more skilled adversary, it would have ended differently, but thats another story.
You almost had him. Lets looks at the factors which let the P51 off the hook:
Firstly, your gun-defensives. There's two things i can mention here. The actual defensive tactics you employ, and the need to be more cohesive: eg thinking of it as not just do a defense, but as a whole plan to get you into a firing position which just so happens to involve a guns-jink. It's a mindset change. You should not look at just avoiding getting shot and after its performed then think about how to saddle up. You should do something which does both simultaneously. You would be suprised to learn how little is actually needed to avoid getting shot. Think about how hard it is to actually hit a moving target in a moving platform. How many factors have to be perfect for it to work? Now, how many factors can you change to spoil their chance of hitting you without resorting to huge energy-sapping left-right high-g break-turns? Less than you would think. Don't think of the guns defensive as an isolated phase of a fight. Think of it as a moderation of your attack plan. Don't do any e-wasting move without a plan on how to get the most from it. Do as little as possible to get the maximum result.
I'll give you a suggestion to try out. Lets modify you're existing guns-defense: which appears to consist of a hard right break turn, then when you notice the other guy isnt turning with you, you hard break back into him. While this may seem instinctive, its far from optimal. Firstly, think about what you're actually doing here? You're actually attempting to cause your opponent to overshoot so you can take advantage of him being in front of your guns for a change, right?? Well, unless you can cause the overshoot AND be in a position to take advantage of it, its fairly pointless. So lets modify your tactic to be: 1, more 3-dimensional, and 2, to take advantage of some known facts (specifically, that fast aircraft cant turn as tight as slower aircraft).
Making your move more 3 dimensional means lets use both the horizontal plane and vertical planes all at the same time. Eg dont just break in one plane, use both, and constantly change the plane of maneuver. This makes you a whole heap harder to anticipate and pull lead on to hit - if not next to impossible. A barrel-roll is a good example. When you (in your film) break just in the horiz plane, you are turning away from your target and opening up distance. Distance you have to close back again if you want to have a crack at him as he overshoots. Since you have such a tiny window to fire (<400) you cant afford to get too far away from them.
Also, if you're being attacked from the rear by a faster BnZ type attacker you can be fairly certain that an overshoot *will* occur, and you just have to avoid eating lead and be in a good position to take advantage of the overshoot. You dont have to break hard and wait to see if they will overshoot before reversing, you pretty much know they will, so you can reverse much earlier than you think, as long as you
out of plane with your attacker. Earlier you reverse the closer you stay to them, and the closer you will be when they pop out in front - perfect for showering them with lead. So stay as close as you can while still avoiding copping some lead yourself and plan for the overshoot and be ready to squirt some lead out. Too early tho and you'll either tip your hand or turn right in front of them.
So, my suggestion is to do a mild break left (or right) which will encourage the enemy to pull lead to try shoot you. Now they are in lead-pursuit and closing the gap extremely fast, now just level off and pull up simultaneously and then roll back the other direction with some elevator to perform a barrel-roll around your attacker. The trick is to not do it as separate steps, but all as one smooth counter. It will be a break followed by a barrel-roll in the opposite direction to the break. There's next to no way he can follow if hes faster than you, let alone pull enough lead to shoot. Next is the tricky bit, aligning your nose to point where you anticipate he will fly through and get it there. This is another out-of-plane maneuver. Now your staying close, but avoiding getting, shot. You're already planned and executing your offensive all at the same time. You've set the trap and they've walked into it. If your lucky you will score a hit or saddle up. This is an example - not the best, but should point you in the right direction:
http://www.my2cents.co.nz/AKUAG/TheVault_Files/FilmDetails.aspx?name=barellroll_defense.zipOk, also your gunnery let you down in a couple of places too. There's no easy fix for this except practice, practice, and more practice. If you're up for a challenge, try turning tracers off. Now you will go through gunnery hell for a few weeks of totally missing everything, but it will come right again - trust me, and then some! When i did this years ago, i couldnt hit a thing, but slowly it got back to normal, and then surpassed my old percentages and has really helped my gunnery HEAPS. YMMV, and you need a lot of perseverance.
Lastly, you simply aren't being aggressive enough. There was at least 2 occasions in the film where you could have followed the mustang up and got a good shot off but you didnt. Knowing when you can and when you cant push the attack comes down to how well you can judge relative E stakes. When you know you have the E to push home a kill, do it. But if you dont know that you do have enough, then its a wasted oppurtunity - one that you may regret. Experience tends to lead to better E 'reading' skills.
You wore him down, but failed to push home the hard won gains, through engineering an overshoot you could have capitalized on.
Heres a film of me in a P40 being picked on by a FW190-D with more E.
http://www.my2cents.co.nz/AKUAG/TheVault_Files/FilmDetails.aspx?name=P40Evs190D.zip
