The LBE Unlimited Ready Build Kit (brand part number AR137RBK) is a compact AR-15 upper build kit centered on a premium 13.7-inch Cold Hammer Forged barrel chambered in .223 Remington/5.56 NATO. Built by LBE UNLIMITED for a pistol-length gas system, this kit ships as a complete upper receiver with a free-floating handguard, gas block, and gas tube already installed alongside the CHF barrel. Cold hammer forging produces a denser, more durable bore than a button-rifled barrel, giving this kit a genuine step up in longevity for a close-quarters AR build.

Key Specifications

• Barrel length is 13.7 inches, cold hammer forged for durability.
• Chambered in .223 Remington/5.56 NATO.
• Runs a pistol-length gas system for a compact, close-quarters build.
• Ships as a complete upper receiver ready to mate with a lower.
• Handguard is free-floating for improved accuracy potential.
• Includes a matched gas block and gas tube installed as part of the assembly.
• Marketed for AR pistol or short-barreled rifle builds given the sub-16-inch barrel.
• Precision-machined construction is engineered for durability and high performance.
• Sold as a complete Kit rather than a bare barrel alone.

Frequently Asked Questions

Does this kit include a bolt carrier group? This kit is sold as a barreled upper assembly; confirm current BCG inclusion on the listing before ordering if you need one.

Can I build an SBR with this kit? This upper is sold without a lower receiver. Because the barrel is under 16 inches, pairing it with a shouldered rifle-configured lower without an approved NFA registration would create a Short-Barreled Rifle; it is legal to build as a pistol on an unregistered lower or as a registered SBR.

Buy the LBE Unlimited 13.7-inch Ready Build Kit

Get a close-quarters-ready AR-15 upper built around a durable hammer-forged barrel. Order this AR-15 upper from our Lubbock, Texas gun shop for fast, insured shipping to your door.