FN America builds the battle-ready machine guns that U.S. military forces depend upon around the world, and they've been building combat-proven platforms for more than 100 years. Now, you can benefit from the company's expertise and manufacturing prowess by getting your hands on one of its hammer-forged M4 carbine barrels. The use of cold-hammer-forging instead of button-rifling in these FN M4 carbine barrels means that they have a level of durability that's unsurpassed in any other barrel design. These barrels are designed to take the punishment of fully automatic fire without skipping a beat, so they'll handle whatever you can throw at them. Each barrel is treated with a manganese-phosphate finish to prevent corrosion, and M4-style feed ramps ensure reliable feeding and function in your mil-spec receiver. After manufacturing, these FN M4 carbine barrels are magnetic-particle-inspected to ensure the metal is free of any flaws or stress points. A chrome-lined bore and chamber ensures corrosion- and heat-resistance. The barrels are available with carbine-length gas systems in 14.5- and 16-inch lengths and feature a twist rate of 1:7 inches.