The G3 system is 'roller-delayed blowback' operated, as you know. It's not very *much* delayed, only barely enough to get the pressure in the chamber down to marginally safe levels before unlocking the bolt head, while the bolt carrier actually accelerates backwards even faster separately from the bolt head. As a result, there's not exactly a lot of mass in the operating mechanism to suck up the recoil, nor is there gas redirection to reduce recoil and the bolt starts its cycle the millisecond the round fires.
The FAL on the other hand uses a gas piston system and a tilting bolt, which makes for a very interesting felt recoil reducer and doesn't allow the bolt to start cycling until the bullet passes the gas tap towards the end of the barrel, so the recoil impulse has to try to move the entire mass of the rifle for quite a while. FALs are heavier than their G3 counterparts, too.
