To the OP's original concern about the original 16's failing in combat.
It was not due to the rifle, it was due to a decision by a pollytickian to save money.
Defense Secretary Robert McNamera(sp) decided to:
1-change the powder specifications to use surplus powder from the Korea era. The stick powder that was originally spec'd out was fairly clean burning but the ball powder that it was changed to fouled horribly.
2-not issue cleaning kits. It was claimed that the rifle was "self cleaning".

The forward assist was added as a "fail safe".