 This opening method causes a suboptimal iron sight line as the rear sight element is mounted on the lower receiver and the front sight element of the sight line is mounted on the upper receiver/barrel and hence are fixed to two different movable subassemblies.The sight radius for the FAL 50.00 and FAL 50.41 models is and for the 50.61 and FAL 50.63 models .FAL rifles have also been manufactured in both light and heavy-barrel configurations, with the heavy barrel intended for automatic fire as a section or squad light support weapon.