Until the early 1990s, the AR-15 generally came in just one caliber. Now, nearly 30 years later, its cartridge evolution has closed the gap with similar short-action designs.
Although the semi-automatic M4-style carbine has dominated the AR market for many years, there is growing interest in ARs more akin to the original design. Why? The rifle-length AR may be your best bet when it comes to ballistics, reliability and durability.
In the past I've heard some of the good folks at Sturm, Ruger & Co. say they work for a gun company, not a components company.