Special ammo, like that NM, was packed in 20 round boxes; the shooters had to load their own clips (5 or 8 round). In the 1950's we also got ball ammo in boxes for training and the troops who were not on the line loaded clips.
But AFAIK, all combat troops got ammo in clips in bandoliers, packed in "spam" cans. Normally it was Armor Piercing, not ball, since it was common to have to fire at light vehicles or obstacles of various types and the higher velocity of the AP gave better results. Actual armor piercing was not common as firing at a tank with a rifle or rifle caliber machine gun was rather pointless.
It was done, though. There is (or used to be) a German tank turret at Aberdeen with a couple of dozen AP cores stuck in it. It looked like a hedgehog.