The first semi-automatic rifle probably was the Italian Cei-Rigotti, developed in 1900 CE, though it was ignored by the military.
Other countries developed experimental models too; none of them was adopted on a wide scale.
That changed in World War II, when the Germans recognized the need for an assault rifle.
They observed that most firefights happened at ranges of less than 400 meters
and that most contemporary long-range bolt action rifles where therefore overpowered.
They envisioned a new type of gun that would combine the range and accuracy of a rifle and the firepower of a submachine gun.
In 1943 CE they came up with the M43/44, later renamed to Sturmgewehr 44, the first true assault rifle.
The Red Army, when confronted with this new weapon, had Mikhail Kalashnikov develop their own,
the Avtomat Kalashnikova model 47, also known as AK-47.
Though today overtaken by newer models, it is still the most popular assault rifle in the world because of its simplicity and reliability.
In the west the the standard was set by the Armalite AR-15.
Assault rifles tend to have shorter and lighter barrels than traditional bolt-action rifles and have a stock to reduce recoil.
This makes them easier to carry and to handle, though on the downside they have less firepower.
Their main advantage is that they are capable of selective fire, handling at least two of the following modes:
- Semi-automatic: one round per pull of the trigger
- Burst: a short burst of several bullets
- Fully automatic: a steady stream of rounds until the trigger is released or ammunition runs out
Semi-automatic + full automatic is the most common; some weapons can also fire bursts.
Since the 1950's CE there has been some evolution in assault rifle design.
Armies are still busy figuring out the ideal caliber for them, swinging back and forth between small high velocity ammunition and larger lower velocity bullets.
In 1977 CE Steyr produced the first bullpup rifle, the Steyr AUG, though experiments with the concept had been going on since the 1950's CE.
In bullpup firearms, the firing mechanism is located behind the trigger, reducing weapon length and weight.
This makes the weapon easier to handle, though it reduces accuracy.
Bullpup assault rifles have become very popular, though have not completely replaced more traditional models.
Because of their flexibility, assault rifles have largely replaced rifles and submachine guns.
Today they are the most common type of infantry weapons.