0-12 IRRC (plus the gas plug that could be set of grenade launcher) and no gas back or bleed off. (Itβs been a while since I fiddled with one)
The other very significant issue was the stock.
The M16 series is a straight line recoil, straight line stock.
The FAL did not have straight line recoil (breach block and carrier moved straight line but the tail went down at a 25ish degree angle - and the wood stock was inlet β so you could end up eating the stock fairly unpleasantly if you had the wrong length of stock.
And the Chipmunk Cheeks became famous from it.
The CAF had 4 stock lengths (Short, Normal, Long and XL) , but very very few units ever actually fit the rifles to people.