My main theme in the OP was the unexpected (at least for me) difference between the .303 and the .50, I fell into the trap of linear comparison whereas the callibre is a linear measurement of a three dimensional object, or two actually, the projectile and the cartridge. With both being considerably larger in terms of mass and volume in the case of the .50 cal (not merely 20% larger as the linear measurement might suggest) it's no wonder they pack such a punch, or conversely, if you take the author's point (and he flew and fought in the Battle of Britain) the .303's were in many cases ineffective.
As for the outcome of the battle had the Brit fighters been equipped with .50's (had that been possible) I guess it would depend on a review of statistics, e.g. if 50% of the intercepts by the RAF resulted in ineffective but accurate strikes on Luftwaffe a/c, it would be fair to presume that .50 cals might conceivably have doubled the RAF kill tally, unless there was some argument as to why the .50's would have also been ineffective. The author flew his share of sorties, had the opportunity to talk with other pilots at the time (and after the battle) and has come to the conclusion that indeed the provision of .50 cals in the Spit's and Hurricanes would have significantly shortened the battle in favour of the RAF.
There are many other factors brought to light in his book, most of which he uses to support his own personal view that gross mismanagement at the Air Staff level both before and during the battle needlessly cost the RAF hundreds of lives and put the country at risk. One of his more important criticisms (in my view) is the failure to mount a spoiling attack on the gathering Luftwaffe across the channel, and I think it is a fair point. Suprise attacks on newly occupied airfields would have almost certainly cost the Luftwaffe dearly not only in terms of a/c and personel but also important infrastructure. This same tactic was used against the RAF with great success, and but for the switch to the bombing of cities the battle might easily have gone the other way.
Add to this the need for more and better training in gunnery for fighter pilots (which could easily have been provided) better combat tactics (which could easily have been copied from the Luftwaffe as far back as the Spanish Civil War) more use of experienced Battle and Blenheim pilots as replacements instead of using pilots straight out of training units, repositioning of the Spitfire and Hurricane squadrons in the north of the country to the south (replacing them with Blenheims etc which were basically left to rot on southern airfields, taking up valuable space and resources) and the list goes on, much of it difficult to fault. All of his arguments rest on well tested doctrines of warfare, but no doubt there are opposing views worth investigating.
Anyway, a cracking good read and I highly recommend it.
