I've fired plenty of FAL's in full auto. I've noticed the shorter barreled ones have less recoil than the longer barreled ones do. I guess the lower muzzle velocity produces less recoil. If there was a muzzle brake a shorter barrel might have more gas for the muzzle brake effect. The slight additional forward weight of the longer lightweight FAL barrel isn't enough to counter the effects of the increased muzzle velocity, and the higher velocity produces more recoil.