The carbine had a tendency to jam, not a desirable trait in close combat. It also was light, and more easily affected by grit than other, heavier weapons. They were in the assault, pushing hard to take high ground, and overrunning Chinese defensive positions intent on keeping the assault going. Then out of the corner of his eye, Dave caught sight of a wounded Chinese soldier rising up behind him. He wheeled to fire his carbine, and the weapon jammed after one erratic round.
Time is one of the several enemies in such circumstances.
Slow reaction is another. Allies are training, adrenaline, and practice at clearing jammed weapons. Dave was able to react, clear the jam, and fire before the Chinese soldier could take aim. From 15 feet away Dave Hughes' second round was more accurate. He killed the enemy soldier.