FN America AR-15 Mid-Length Barrel 16in 5.56 NATO | 20-100041

Overview of the FN America AR-15 Barrel | 20-100041

Built for a reliable mid-length AR-15 build

Building or refreshing a mid-length AR-15 and want a barrel you can trust to hold zero and feed round after round? The FN America AR-15 Barrel (MPN 20-100041) brings real military heritage to your upper. FN America is the U.S. maker behind many of the nation's service rifles, and this 16-inch 5.56x45mm barrel is cut and finished to the same standards.

Machined from U.S.-sourced Chrome Moly Vanadium steel and coated in a matte black manganese phosphate finish, the barrel resists corrosion and heat erosion through long range sessions. Its mid-length gas system softens recoil for a smoother-shooting rifle, while the chrome-lined chamber and M4-style feed ramps keep 5.56 NATO and .223 Remington rounds chambering cleanly.

Home builders, competitive shooters, and agency armorers reach for the 20-100041 because it pairs trusted FN quality with a straightforward 1/2 x 28 threaded muzzle and a 1:7 right-hand twist.

Key Features

• Caliber: Chambered in 5.56x45mm NATO and compatible with .223 Remington
• Barrel Length: 16 inches in a Government / M16 profile
• Gas System: Mid-length for a longer dwell time and softer recoil
• Material: U.S.-sourced Chrome Moly Vanadium steel built to Mil-B-11595E
• Finish: Matte black manganese phosphate that resists corrosion and oxidation
• Rifling: Button-rifled bore with a 1:7 right-hand twist
• Chamber: Chrome-lined chamber and bore with M4-style feed ramps for reliable feeding and longer barrel life
• Muzzle: 1/2 x 28 threads accept standard muzzle devices
• Gas Journal: 0.750 inch diameter under the gas block seat
• Quality Control: Each barrel is High Pressure Tested (HPT) and Magnetic Particle Inspected (MPI)
• Installation: FN recommends fitting by a qualified, trained gunsmith

Specifications

Compatibility

This barrel drops into standard AR-15 and M16 uppers chambered for 5.56 NATO and uses a common 0.750 inch gas block. It requires a mid-length gas tube and a handguard long enough to clear the gas block at the mid-length position. The 1/2 x 28 muzzle threads accept common flash hiders, muzzle brakes, compensators, and 5.56 suppressor mounts.

It is not set up for carbine-length or rifle-length gas without swapping the gas tube, and it is not intended for .300 Blackout, .224 Valkyrie, or other non-5.56 cartridges. A gas block, gas tube, handguard, muzzle device, and barrel nut are sold separately.

Intended Users

Home gunsmiths and hobbyist builders assembling or upgrading a mid-length AR-15 will find this an easy fit for a standard upper. Competitive and recreational sport shooters gain FN accuracy and the softer recoil impulse of a mid-length gas system. Law enforcement armorers and agency builders maintaining patrol carbines can use it as a military-grade replacement barrel, and self-reliant civilians and preppers can build a dependable defensive rifle around it.

What's Included

• One (1) FN America AR-15 mid-length barrel, MPN 20-100041

This ships as a bare barrel. A gas block, gas tube, handguard, muzzle device, barrel nut, upper receiver, and any shims or crush washers are not included and must be purchased separately.

Shipping Restrictions

This item is a firearm barrel (a rifle part). It ships as a standard component under federal law, but some states restrict where barrels and threaded parts can be sent. Please review before ordering:

• California: We cannot ship this barrel directly to a California address. Under California law, effective January 1, 2026, firearm barrels must be transferred in person through a licensed California firearms dealer (FFL). Contact us to arrange an FFL transfer.
• Illinois: We cannot ship threaded barrels to Illinois addresses.
• Massachusetts: We are unable to ship this firearm part to Massachusetts addresses.
• Other states with "assault weapon" feature laws (including NY, NJ, CT, MD, HI, WA, DC, DE, RI, VA, and CO): Restrictions may apply to threaded barrels and how they are used in a build. Please confirm your state and local laws before ordering.

You are responsible for knowing and following all federal, state, and local laws that apply to your address. If an order cannot be legally shipped to your location, we will cancel it and issue a refund or store credit.

Law enforcement agencies and licensed dealers: Exemptions may apply. Contact us with your agency or FFL documentation, and we will help arrange a compliant transfer.

Questions? Reach our team by phone or chat before you order, and we will confirm whether we can ship to you.

Available at WCUniforms

WCUniforms is a veteran and family-owned specialty retailer serving law enforcement, military, and serious shooters with tactical gear and firearm components. As a former law enforcement, EMT, and veteran-owned business with an A+ BBB rating, we back every order with real phone and chat support and same-day shipping on most in-stock items (Monday through Friday). Shop the FN America 20-100041 with confidence at wcuniforms.com.