CMMG AR15 Gun Builders Lower Parts Kit
The CMMG AR-15 Gun Builders Lower Parts Kit (55CA601) gives you the core hardware needed to finish a stripped AR-15 lower receiver without paying for the parts most builders swap out anyway. It includes the bolt catch assembly, magazine release, safety selector, takedown and pivot pins with detents and springs, and hammer/trigger pins — but intentionally leaves out the trigger guard, fire control group, and pistol grip so you can install your own preferred upgrades. All components meet or exceed mil-spec tolerances and are compatible with standard AR-15 and Mk4 lowers. Ideal for custom builders running aftermarket triggers, grips, and trigger guards on a 5.56, .223, or 300 BLK build.
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- SKU
- 55CA601
$45.45
Description
Features
- Mil-Spec Construction — Every component in the kit meets or exceeds mil-spec dimensions and tolerances for reliable fit in any standard AR-15 lower receiver.
- Builder-Focused Configuration — Intentionally omits the trigger guard, fire control group, and pistol grip so you can drop in your preferred upgraded parts without paying for components you'll replace.
- Complete Takedown Hardware — Includes the takedown pin, receiver pivot pin, two detents, and two detent springs needed to mate your upper and lower receivers.
- Bolt Catch Assembly — Comes with the bolt catch, plunger, spring, and roll pin to complete the left-side bolt hold-open function.
- Magazine Catch Assembly — Magazine catch, spring, and button are included for a proper, mil-spec mag release on your build.
- Safety Selector Group — Ships with the safety selector, detent, and spring to install a standard two-position safety on the left side of the receiver.
- Hammer and Trigger Pins — Two mil-spec retaining pins ready to drop in whichever fire control group you choose to install.
- Black Phosphate Finish — Steel components wear a durable matte black phosphate coating that resists corrosion and matches standard AR-15 furniture.
- AR-15 / Mk4 Platform Compatible — Designed to fit any standard AR-15 or CMMG Mk4 forged or billet lower receiver chambered in 5.56 NATO, .223, 300 BLK, and similar small-frame calibers.
- Made in the USA — Manufactured by CMMG in Boonville, Missouri, backed by the company's reputation for quality AR components.
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Customer Reviews
Top customer reviews
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Good all around LPK, no FCG for those using a drop-in trigger or using a different trigger.It's a good quality mil-spec parts kit. Not much more to say about it. Probably one of the better quality ones, but nothing special.
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Lower partsPerfect fit and works like magic…
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NiceGreat kit. Quality parts from an American company. Color coded bags make it easier for the installation.
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Easy to InstallAll of the parts fit nicely into my build and so far, nothing out of the ordinary. I still need to test fire my rifle, but so far so good.
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Nice lower parts kitThis lower parts kit is great and it was very easy to install
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