The CMMG Gun Builders Lower Parts Kit (brand part no. 38CA61A) supplies the small hardware needed to complete a mil-spec .308/7.62 NATO AR-10/Mk3 lower build, deliberately leaving out the fire control group and other parts builders commonly swap for aftermarket upgrades. CMMG has long been a trusted name for AR-pattern components, and this kit reflects that reputation with correctly sized parts for the larger .308 lower pattern rather than a standard 5.56 AR-15 kit. It’s a practical starting point for anyone assembling a .308 build who wants to control which upgraded parts go in.

Key Specifications

• Chambered for the .308 Winchester/7.62 NATO AR-10/Mk3 lower receiver pattern.
• Package length of approximately 7.5 inches.
• Shipping weight of approximately 0.225 pounds, consistent with a small-parts kit.
• Sold explicitly without the commonly upgraded parts such as the fire control group, letting builders choose their own.
• Manufactured by CMMG, a name trusted for mil-spec-consistent AR components.
• Packaged as a complete small-parts kit rather than individual loose pieces, reducing the chance of a missing part mid-build.
• Designed to work with a range of aftermarket AR-10/.308 fire control groups.
• Rounds out an AR-10/Mk3 lower build alongside a separately sourced fire control group.

Frequently Asked Questions

What platform does this kit fit? Mil-spec .308/7.62 NATO AR-10/Mk3 lower receivers.

Does this include a fire control group? No — it’s sold minus the commonly upgraded parts so you can install your own.

Buy the CMMG Gun Builders Lower Parts Kit

Complete your .308 AR-10/Mk3 lower build with genuine CMMG hardware. Order it from our Lubbock, Texas gun shop for fast, insured shipping, and browse our full AR lower parts kit selection.