CMMG AR-15 Gun Builders Lower Parts Kit - No Grip or Fire Control Group (FCG)

Building an AR-15 from a stripped lower receiver means sourcing every individual spring, pin, and detent—a process that gets tedious fast if you're buying parts one at a time. The CMMG AR-15 Gun Builders Lower Parts Kit cuts that friction by bundling all the internal components you need to finish your lower receiver, minus the fire control group, grip, and trigger guard so you can choose those separately. Whether you're assembling your first rifle or your tenth, this kit keeps the small parts organized and gets you closer to a complete lower in fewer orders.

CMMG has built a solid reputation supplying OEM parts and uppers to major manufacturers, so these components meet the same spec and quality bars used in production rifles. The kit includes all the pins, detents, springs, and catches that make your safety selector, bolt catch, and magazine release function reliably. You'll handle the fire control group and grip as a separate decision—letting you pair this kit with the trigger and ergonomics that fit your shooting style and budget.

This is the go-to choice for builders who want a complete, no-nonsense parts list without overpaying for redundant kits or wasting time chasing down individual pieces. Stock up for your next build, or keep one on hand as a backup.

What's Included

• Takedown pin
• Receiver pivot pin
• Takedown pin detents (qty. 2)
• Takedown pin detent springs (qty. 2)
• Hammer and trigger pins (qty. 2)
• Safety selector
• Selector detent
• Magazine catch with spring
• Magazine release button
• Bolt catch with plunger
• Bolt catch spring and pin
• Buffer retainer with spring

Frequently Asked Questions

What do I need to complete the lower receiver after using this kit?

You'll need to source a fire control group (trigger, hammer, and sear), a grip, and a trigger guard separately. This kit provides everything else required to assemble a functional lower receiver.

Can I use this kit with any AR-15 lower receiver?

Yes, these parts are standard AR-15 spec and will work with any mil-spec lower receiver.

Are these OEM parts or aftermarket?

CMMG manufactures and supplies components to major firearms manufacturers. These parts meet OEM specification and quality standards.

Is this kit suitable for a first-time builder?

Absolutely. Having all the small parts organized in one kit makes the assembly process much simpler and reduces the risk of missing a detent spring or pin.