CMMG 55CA65A AR Pistol Receiver Extension Kit for AR-15 Platforms

The CMMG 55CA65A AR Pistol Receiver Extension Kit for AR-15 platforms gives you the core components you need to assemble a complete pistol lower group. If you're building an AR-15 pistol and already have a lower parts kit picked out, this receiver extension assembly bridges the gap between your vision and a finished firearm. CMMG designs these kits to work within the AR-15 ecosystem, letting you focus on the rest of your build without worrying about compatibility headaches.

Building an AR pistol is a popular project for shooters who want a compact, maneuverable firearm for home defense, short-range training, or specialized competition. A quality receiver extension kit is essential—it houses the spring and buffer that manage bolt carrier group movement and recoil impulse. This kit from CMMG includes what you need to get that part of the build right, so you can move forward with confidence.

Whether you're a first-time builder or you've assembled several AR-15s already, having a reliable kit from a trusted manufacturer takes one decision off your plate. Pair this with your chosen lower parts kit and lower receiver, and you're well on your way to a functional pistol that shoots the way you want it to.

What's Included

• Pistol receiver extension (buffer tube)
• Carbine action spring
• Carbine buffer

Frequently Asked Questions

What lower parts kit do I need to pair with this kit?

This receiver extension kit is designed to work with any standard AR-15 lower parts kit. Once you've selected your preferred lower parts kit, install the components from this kit into your lower receiver to complete the pistol lower group assembly.

Is this kit compatible with AR-15 platform builds?

Yes. The CMMG 55CA65A is designed for AR-15 platforms. It follows standard AR-15 specs, so it will work with any compatible lower receiver and parts.

Do I need any special tools to install this kit?

This kit contains the receiver extension, spring, and buffer—the main components that go into your lower. Installation typically requires basic gunsmithing tools and familiarity with AR-15 assembly. If you're new to building, consult an assembly guide or have a qualified gunsmith handle the work.