A further factor was that the French already had a 13.2mm HMG in production, by Hotchkiss. It was used for naval AA, airfield AA by AdA (France had a very goofy split of land AA responsibility among multiple organizations), and was prototyped for vehicle mounted AA by the Infantry. The Hotchkiss gun was magazine fed rather than belt (a fundamental design error it had in common with the Hotchkiss 25mm autocannons), and was a bad enough design that it was mechanically limited on cycling rate rather than thermally, so was not suitable for aircraft use. But those details were irrelevant to the French government, which would not consider buying from FN because French workers already were making "the same" weapon and everything was about maximizing employment in existing French companies.
As noted in other posts, FN had developed in the late 1930s an explosive 13.2mm round that they had shown via testing to be very effective against aluminum-skinned aircraft...arguably even more so than 20mm because of the greater RoF and therefore likely greater number and location of hits. FN however found it very difficult in the sociopolitical environments and military stress of that period to get objective consideration of their weapon system. If I recall correctly, they had made two tentative sales, to Romania and Sweden. I don't know if any sales got as far as deliveries.
Yes, but.
France and Britain were partnered in the French British Purchasing Commission, actively seeking to spend large amounts of French and British funds to buy USA manufactured warplanes among other weapons. US aircraft designs were transitioning in the late 30s from .30 caliber MGs...with mounting locations, controls and feed arrangements that with some trouble could be converted to .303 or 7.5mm...to .50 caliber. It wasn't practical to convert .50 caliber mount locations to .303 or 7.5mm, and it certainly wasn't practical to convert them to 20mm. So there was an awareness that any aircraft they bought after the P36 generation (i.e. the French H75) would be engineered for .50 caliber armament. The FN-made Browning 13.2mm was a drop-in replacement for the US Colt-made Browning .50 caliber (i.e. 12.7mm). Nothing else available to Britain or France would have offered that assured functionality.
So notwithstanding that they were "happy", they should have been aware that change was coming, one way or another.
