Vietnam War troops hated the M16 and dubbed it the "Mattel 16" because it felt more like a toy than a battle rifle.
"We called it the Mattel 16 because it was made of plastic," said Marine veteran Jim Wodecki in the video below. "At that time it was a piece of garbage."
It weighed about half as much as the AK-47 Kalashnikov and fired a smaller bullet – the 5.56 mm round. In short, the troops didn't have faith in the rifle's stopping power.
Compounding the M16's troubles was its lack of a proper cleaning kit. It was supposed to be so advanced that it would never jam, so the manufacturer didn't feel it needed to make them. But the M16 did jam.
"We hated it," said Marine veteran John Culbertson. "Because if it got any grime or corruption or dirt in it, which you always get in any rifle out in the field, it's going to malfunction."
The troops started using cleaning kits from other weapons to unjam their rifles.
"The shells ruptured in the chambers and the only way to get the shell out was to put a cleaning rod in it," said Wodecki. "So you can imagine in a firefight trying to clean your weapon after two or three rounds. It was a nightmare for Marines at the time.
Towards the end of 1965, journalists picked up on mounting reports of gross malfunctions. The American public became outraged over stories of troops dying face down in the mud because their rifles failed to fire, according to a story published by the Small Arms Review.
Thankfully, the reports did not fall on deaf ears. The manufacturer fixed the jamming problems and issued cleaning kits. The new and improved rifle became the M16A1.
This video features Vietnam Marines recounting their first-hand troubles with the M16: