The AR-series of rifles, such as the AR-15, AR-10, M4, and M16 variants are the second most common rifle ever designed, after the AK-47. They are available in a myriad of different calibers, with the most common and plentiful being in the 5.56x45mm NATO. Today, the AR-15 is the best selling rifle in the United States, with the most popular variant being the 16 inch barrel with the 5.56 caliber. They are also built by a wide number of manufacturers, with Colt, Daniel Defense, SIG Sauer, Springfield, Smith & Wesson, and Ruger being among the most prominent.
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