Classic Firearms compares the AR-15 and the Sig Sauer MCX Spear LT, covering their histories, mechanisms, and shooting performance. The AR-15, developed in the 1950s, utilizes a buffer system, while the Sig MCX Spear LT, a lighter version of the military's MCX Spear, features a short-stroke piston system. Both rifles are chambered in 5.56, but other calibers are available. In their shooting tests showed comparable recoil, but the Spear LT produced less gas blowback and a cooler handguard. Whilst the AR-15 is highly customizable, the Sig MCX Spear LT is praised as a "phenomenal weapon system."