He finished his 2nd Tour before the M16A1 was widespread, not a Fan of the original. The original mags had serious feeding problems too, loading 18+, the springs wouldn't hold up and there would be feed issues. Powder choice would be the same trouble, Korea got hot&humid Summer and cold Winter, so jams galore.
To be fair, he also said the Carbines had magazine issues as well, but not as bad as the M16.
I think when asked, what if they had only the M16 in Korea over the Garand, BAR and Carbines, he said he'd be dead.