No it wasnt. The FAL was originally designed to fire the German 7.92x33 Kurz round.
nope, the first fal type design used the full sized 7.92 german round, then the "FN No. 1 Carbine" was in 7.92 kurz, but the first "Lightweight Automatic Rifle, FAL" was made in 280, but your right, the first thing that looked like an fal was in 7.92k
R. Blake Stevens goes into great detail on the development of the round, including the cases thought up in .33 in, .30 in, .27 in, and .25 in, in bases 2.0x, 1.8x and 1.6x the bullet diameters with various pentration ratings using different cores and estimating chamber pressures, number of rounds a soldier could carry, and the total weight of the rifle. the brits went much further into ballistics, ergonomics and total system planning than the americans ever did, by starting with the ammo, and optimizing it, rather then using the same thing cause "it worked ok before dinnit?" and trying to make a weapon for it.
imagine if you could buy a round that had a flat trajectory like 5.56, and all the armour penetration of 7.62, and had all the reliability benefits of larger gas ports, tubes, etc (harder to clog a big hole than a small one) but could still have it in a 7 pound AR type rifle
I've done a fair bit of research into that, and others including the 'new' 6.8 
