4.5″ 9mm AR15 Barrel – 4150 CMV Nitride AR9 Barrel with 1/2×28 Threads

Building a compact AR9 pistol, 9mm PCC, or short-barreled 9mm upper starts with choosing the right barrel. Our 4.5″ 9mm AR15 barrel is designed specifically for blowback-operated AR9 platforms, offering a durable, accurate, and compact option for builders who want a short, lightweight setup without sacrificing reliability.

Unlike traditional AR15 rifle calibers such as 5.56 NATO, a 9mm AR barrel does not use a gas system, gas port, or traditional star chamber design. AR9 platforms operate using a simple blowback system, meaning the barrel is purpose-built around the unique requirements of pistol-caliber AR builds.

This barrel measures 4.5 inches from end to end. Barrel length is measured from the bolt face to the muzzle, which is the industry standard method used to determine firearm barrel length. Because 9mm AR platforms do not utilize a locking bolt and star chamber like traditional rifle calibers, the chamber and feed geometry are different.

The barrel features a conical feed ramp designed for smooth cartridge presentation and reliable feeding with common 9mm ammunition. Whether you are assembling a dedicated AR9 upper or upgrading an existing 9mm PCC, this barrel provides the foundation for a dependable build.

Built from 4150 CMV Steel with Nitride Finish

We manufacture this AR9 barrel from 4150 Chrome Moly Vanadium (CMV) steel, a proven barrel material known for strength, durability, and excellent service life. The barrel receives a corrosion-resistant nitride treatment that increases surface hardness, improves wear resistance, and provides a smooth, easy-to-maintain finish.

Compact 4.5″ Length for AR9 Builds

A short 4.5 inch 9mm barrel is an excellent choice for compact AR9 pistols, home-defense setups, backpack builds, and suppressed applications where a shorter overall package is desired.

The compact profile helps reduce overall firearm length and weight while still providing the performance expected from a 9mm PCC platform.

Threaded 1/2×28 Muzzle

The muzzle features standard 1/2×28 threads, allowing compatibility with many common 9mm muzzle devices, compensators, and suppressor mounts.

Product Features

• Caliber: 9mm Luger / 9x19mm
• Platform: AR15 9mm blowback / AR9 / 9mm PCC
• Barrel Length: 4.5″ (measured bolt face to muzzle, will not extend past a 4″ handguard, it’s short)
• Material: 4150 Chrome Moly Vanadium (CMV)
• Finish: Nitride
• Twist Rate: 1:10
• Muzzle Threads: 1/2×28
• Feed Ramp: Conical feed ramp
• Gas System: None (blowback operated)
• Gas Port: None

Designed for Your Next AR9 Build

Whether you are building a compact 9mm AR15 upper, upgrading an existing AR9 barrel, or assembling a dedicated pistol-caliber carbine, this 4.5″ 9mm barrel provides the quality materials and purpose-built design needed for a reliable build.

From compact AR9 pistols to lightweight PCC configurations, this barrel is engineered for builders who want a durable, American-made foundation for their 9mm platform.