M16 Assault Rifle
In 1955 the US army demanded a new weapon as standard issue to troops in the field. Like a submachine gun it had to be lightweight and capable of fully automatic fire. But, like a rifle it would also have to hit and penetrate a helmet at 500 yards. The new hybrid weapon would be called the "Assault Rifle". An early contender, the M14 was, effectively, a World War II rifle modified for full automatic fire. Unlike the Tommy Gun, it used high-power rifle ammunition, heavy 7.62mm shells packed with powder. Conventional wisdom held that this was the best way to guarantee accuracy at 500 yards.
But, a heavy cartridge means heavy recoil and the low stock piece makes the M14 twist on recoil rendering full automatic fire very inaccurate.
In the mid 1950s weapons manufacturer Armalite appointed a brilliant chief engineer named Eugene Stoner. Stoner was convinced that for long-range automatic fire both gun and cartridge would have to be completely transformed.
The M14 Rifle
Stoner straightened the gun stock, placing it in line with the barrel. Now the recoil goes directly along the line of sight and the gun stays on target. Stoner raised the sights to bring them up to eye-level. The result was the distinctive profile of one of the 20th century's iconic weapons - the M16 Assault Rifle.
The M16 Assault Rifle
It had a truly space-age look and feel. Eugene Stoner used aluminium alloy for many vital components, the plastic hand guard and butt-stop earned it the nickname the "Black Rifle".
The most controversial innovation was not in the rifle however it was in the cartridges. Stoner threw away the heavy 7.62mm ammunition of the M14 and replaced it with a slim line cartridge of just 5.56mm. The weight saving meant that troops could carry twice as many fully-loaded magazines into battle.
But it seemed, to a sceptical army, that the M16 cartridge wasn't heavy enough to take out the enemy. How would th weapon perform in field trials? There's far less kick from the smaller cartridge. The weapon's straight profile means the recoil goes straight back into the soldier's shoulder.
It's far easier to keep the M16 trained on the target, even on automatic. The cartridges penetrate the target helmet fulfilling the specification.
The M16 seemed to be the weapon of the army's dreams and by 1965 it was ready to be fieldedin Vietnam.
Soldiers were still not convinced the M16 would be effective in combat. Some didn't believe the slender cartridge would put a man down and keep him down. But, the Black Rifle was soon spreading terror through the enemy ranks. The new cartridge was punching above it's weight.
The M16 bullet is exceptionally fast, more than 3,000 feet per second. When it strikes human tissue, the lightweight nose slows down while the heavier base maintains momentum. The bullet tumbles end over end creating a huge bending force that it cannot withstand. The bullet fragments, literally explodes, within the body causing dreadful injuries.
CREDITS: All of the above information was taken from the UK's Channel Five "Inventions of War" documentary series.