SVT-40

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The SVT-40 is also known as the Samozaryadnaya Vintovka Tokareva.  The SVT-40 was designed in WW1 but it wasn't built until after WW1 and before WW2.  It is a Soviet Union Semi-Automatic Battle Rifle.  It was used by the Soviet Union, North Korea, and the peoples republic of China.  The SVT-40 wasn't a very common Assualt Rifle during WW1.  The designer of the SVT-40 also designed the tokarev which is a pistol.

M1 Carbine

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The M1 Carbine is a Assault Rifle used by the USA.  It Is a lightweight semi-automatic carbine.  It was a standard US Firearm in the USA Military.  It was widely used by U.S. and foreign military and paramilitary forces, and has also been a popular civilian firearm.  The M1 Carbine was used as an Infantry Squad rifle.  The M1 Carbine was very common among US soldiers in WW1.  It was a very strong weapon and it was used to try and penetrate through the armor on certain tanks used by enemys out on the battlefield. 

AK-47

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The AK-47 is also known as Avtomat Kalashnikova.  It is one of the most widely used assault rifle on the planet.  It was first designed by the Soviet Union by Mikhail Kalashnikov in the 1940's.  The AK-47 was the standard issue assault rifle used by the Soviet Union.  The first Ak-47 was actually designed in 1947, hense the name AK-47.  The AK-47 is very cheap and easy to handle which is the reason that it is the most popular assault rifle on earth.  Many different countries produce the AK-47 and it is used by many different army's.  Over 70 million AK-47's have been built so far.  It has been in service since 1949. 

M16A4

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The M16A4 is the main Assault Rifle used by the US Military.  Armalite purchased the rights to the AR-15 which is a variant of the M16A4.  The M16A1 was the first M16 which was used in the Vietnam war.  Since the Vietnam War the M16 has become the main assault rifle.  It has become the most produced assault rifle in it's caliber.  The United States Air Force took in the AR-15 and it worked pretty well for them so the US Marine Corps made the M16 which was a variant of the AR-15 but since they made the M16 it has become a popular weapon to make many variants from.