The Cobalt Kinetics CK-Pro Upper Receiver Group in 5.56 NATO with a 13.7-inch barrel and black Cerakote finish (Cobalt Kinetics part no. CKPROURG556137BLK) is a complete AR15-platform upper built for shooters who want a mid-length 5.56 build with the same fit and finish as a complete CK-Pro rifle. Every CK-Pro URG in this configuration is hand-built by Cobalt Kinetics’ own gunsmith staff and test-fired for function before it ships. The 13.7-inch barrel gives a balance of maneuverability and sight radius that suits a wide range of rifle and SBR builds, and the black Cerakote finish adds a durable, corrosion-resistant coating over the aluminum receiver. It’s machined to bolt onto any mil-spec AR15 lower receiver.

Key Specifications

• Chambered in 5.56 NATO, the standard AR15 chambering for widely available ammunition.
• Fitted with a 13.7-inch barrel, a popular mid-length option for balanced handling.
• Finished in black Cerakote for a durable, corrosion-resistant coating.
• Assembled and test-fired for function by Cobalt Kinetics’ gunsmith staff before shipping.
• Machined to mil-spec dimensions for compatibility with standard AR15 lower receivers.
• Hand-assembled by Cobalt Kinetics’ own gunsmith staff before shipping, rather than sold as a stripped receiver.
• Ships as a complete upper with the barrel, bolt carrier group, and charging handle pre-installed.
• Includes one Duramag magazine as shipped from Cobalt Kinetics with every built CK-Pro URG.
• Chambered to accept both 5.56 NATO and .223 Remington ammunition.

Frequently Asked Questions

Is this a complete, built upper or a stripped receiver? This CK-Pro URG configuration is a fully assembled, test-fired upper.

Will this bolt onto a standard AR15 lower? Yes, it’s machined to mil-spec dimensions for compatibility with standard AR15 lower receivers.

Buy the Cobalt Kinetics CK-Pro Upper Receiver Group (5.56 NATO, 13.7-inch)

Get a gunsmith-built, test-fired 13.7-inch 5.56 upper ready to drop onto your build. Order it from our Cobalt Kinetics lineup of AR15 uppers, shipped fast from our Lubbock, Texas gun shop.