The AR-15 is a common assualt rifle. Very similar in looks to an M-16, but not exactly.
AR does NOT stand for Assault Rifle, as is commonly believed. AR stands for the original company that manufactured it, ArmaLite. ArmaLite sold their rights to the AR-10 and AR-15 designs in 1959 to Colt.
With a simple barrel and receiver switch, this rifle can fire 14 different calibers and sizes of ammunition, ranging from .22LR to .50BMG.
Completely customizable, this rifle can also be a personal defense firearm at less than 36 inches long, to a sniper rifle over 50 inches.
Standard magazine (or clip, if you prefer) is 30 rounds, but aftermarket 5, 10, 20, 30, 40, 60, 90, and 100 round magazines are available as well, but only the 5 round, non-detachable clip is legal in California. These clips are breech loaded, and do NOT come off. The reason for this is because of the Assault Weapon Ban that The Clinton Administration put into affect, and this method of semi-automatic action slows the loading process and is supposed to reduce murders. All it did was boost illegal weapon sales.
With the modular accessory rail, hundreds of different aftermarket accessories are available. These range from simple, and relatively cheap in price, tac-lights, vertical secondary pistol grips,to night-sights, to bipods, to thermal scopes, to night-vision scopes and infrared scopes beyond normal mag-scopes with somewhere around 20+ compatible scopes. Other accessories are different stocks, from collapsibles to solid body, to skeleton, to adjustables.
These rifles, when sighted in are accurate up to 500 yards, with a range well beyond that.
The semi-automatic feed uses a direct gas impingement system. (If lost with this term, use wiki)
This rifle was designed by Eugene Stoner in 1958 as an updated, lighter version of the AR-10. The design was initially submitted as a new rifle for the US Armed Forces, and is what the M-16 was based off of.
Overall, this is a very effective weapon for home defense, hunting, sharpshooting, and just fun at the range.
Possible calibers for the AR-15 are:
(Yes, the NATO round is different from a .223REM. The NATO round has higher power, and needs mods to the weapon to be fired safely. Commonly confused and called the same as .223REM, because they have the same physical dimensions but different power levels)
(All these .50s are different power ratings and dimensions, but the bullet itself is the same size.)