Rock River Arms LAR-40 A4 40 S&W Mid-Length System AR-15 16" Barrel 30 Round Black Finish Semi Automatic Rifle 40S1855

Designed by Winchester and introduced by Winchester and Smith & Wesson in 1990, the 40 S&W was designed as a "compromise" semiautomatic pistol cartridge that would offer more performance than the 9mm Luger (9x19)…but would produce less recoil and allow higher magazine capacity than the 45 ACP. Few compromises in the firearms world have ever worked as well. From a manufacturing standpoint many pistols designed for the 9mm could be re-engineered to handle the larger cartridge; in a short time it has become a standard issue in the law enforcement community. Using a .400-inch bullet of from 135 to 180 grains from a .850-inch cae, the .40 S&W produces up to 1205 fps, and although recoil is greater than the 9mm, it is easier to shoot than the 45 ACP, and its greater velocity and smaller bullet diameter aid penetration. — Craig Boddington