The AR-15 family of rifles is one of the most prolific and effective in the world. In the guise of the M16 rifle or M4 carbine it has served continuously as the U.S. armed forces issued rifle for over 50 years, and has been adopted by dozens upon dozens of other militaries around the world. It is also widely employed as a patrol rifle by police and government agencies, to say nothing of the more than 15 million AR-15 variants that have been commercially produced in the U.S.
Any system is only as reliable as its weakest component, and a common weakness for a firearm is an inferior magazine. Rifles, including the AR, are no different. The AR has seen many improvements and innovations over the course of its long life, among them many revisions to the design of the magazine. Accompanying the dizzying array of other components and accessories available to a user today, there are over a dozen different types of magazine: constructed of original aluminum, steel or polymer, and each has many unique designs.