CMMG ZEROED Lower Parts Kit – Ambi Safety & Mag Catch, Mil-Spec Trigger, Black Grip, Fits AR-Platform/Mk4 – 55CA642
Upgrade or complete your AR build with confidence using the CMMG ZEROED Lower Parts Kit (S5CA642). Designed for shooters who demand modern ergonomics, ambidextrous controls, and proven reliability, this black lower parts kit includes everything you need to outfit a stripped lower receiver for AR-platform/Mk4 rifles, including an ambi safety selector, ambidextrous magazine catch, mil-spec trigger, and ZEROED pistol grip.
Whether you’re assembling a brand-new rifle, refreshing an older lower, or standardizing your fleet with one high-quality parts kit, the CMMG ZEROED Lower Parts Kit 55CA642 ensures your build starts with a solid, dependable foundation.
Complete Lower Parts Kit for AR-Platform/Mk4 Builds
This ZEROED kit is engineered to work with AR-platform and CMMG Mk4 lower receivers, giving you a high-quality, cohesive set of components designed to function together flawlessly.
Instead of mixing components from different sources, you get a unified, factory-matched kit from a trusted manufacturer—CMMG.
Ambidextrous Safety Selector – Modern Control for Any Shooter
The standout feature of this kit is the ambi safety selector, designed to accommodate both left- and right-handed shooters:
Allows safe/fire control from either side of the receiver
Ideal for left-handed shooters or anyone who trains to shoot from both shoulders
Enhances ergonomics and weapon manipulation under stress
If you’ve ever wanted your AR to feel more intuitive and adaptable, the ambidextrous safety is a major upgrade over a standard single-sided selector.
Ambidextrous Magazine Catch – Faster Reloads, Either Hand
The ambidextrous magazine catch takes your AR controls to the next level:
Provides mag release capability from both sides of the lower receiver
Enables smoother, more efficient reloads for left-handed or off-hand shooting
Great for tactical, defensive, and competitive environments where speed matters
Combined with the ambi safety, this kit makes your AR-platform build truly lefty-friendly and modernized.
Mil-Spec Trigger – Proven Reliability and Familiar Feel
At the heart of the kit is a mil-spec style trigger group, offering:
A reliable, combat-proven design familiar to most AR shooters
Consistent pull and reset ideal for duty, training, and general use
Robust construction aimed at long life and dependable performance
For shooters who prioritize reliability and predictability over ultra-light match pulls, a mil-spec trigger is a smart, durable choice.
ZEROED Black Pistol Grip – Comfortable & Control-Focused
The kit includes a CMMG ZEROED black pistol grip, engineered for comfort and control:
Ergonomic shape designed for secure, natural hand placement
Texturing for improved grip during extended shooting sessions
Clean, low-profile look that complements modern AR builds
This grip gives your rifle a solid, confident feel whether you’re at the bench, on the range, or running drills.
High-Quality Small Parts – Springs, Pins, and Detents
In addition to the major controls, the ZEROED lower parts kit includes the essential small parts needed to complete your lower:
Takedown and pivot pins
Bolt catch and release components
Springs, detents, and pins for proper function
Trigger and hammer pins, magazine catch hardware, and more
Each piece is designed to meet or exceed mil-spec standards, giving you confidence that your lower receiver is built on quality components from the ground up.
(Always follow manufacturer instructions or consult a qualified armorer/gunsmith for installation.)
Perfect for Builders, Upgraders, and Serious Shooters
The CMMG S5CA642 ZEROED Lower Parts Kit is an excellent choice for:
AR builders completing a stripped lower for the first time
Enthusiasts upgrading older rifles with ambidextrous controls
Left-handed shooters who want a more intuitive, user-friendly setup
Training and duty rifles needing dependable, standardized internals
If you demand smooth function and modern ergonomics, this kit gives you a lot more than just the typical “parts bin” feel of generic LPKs.
Clean, Modern Aesthetic with CMMG ZEROED Styling
Beyond functionality, this kit carries the ZEROED styling and quality that CMMG is known for:
Sleek black finish throughout for a cohesive look
Coordinates perfectly with modern black or two-tone AR builds
Helps give your rifle a professional, purpose-built appearance
Whether you’re assembling a duty-ready carbine, a defensive rifle, or a range workhorse, this kit fits right in with modern AR aesthetics.
Key Features – CMMG ZEROED Lower Parts Kit (55CA642)
Brand: CMMG
Series: ZEROED
Model: S5CA642 Lower Parts Kit
Part Number: 55CA642
UPC: 810097502307
Compatibility: AR-Platform / CMMG Mk4 lower receivers
Safety: Ambidextrous safety selector
Magazine Catch: Ambidextrous mag catch
Trigger: Mil-spec style trigger group
Grip: ZEROED black pistol grip
Finish: Black
Why Choose the CMMG S5CA642 ZEROED Lower Parts Kit?
All-in-one solution for AR-platform and Mk4 lower receivers
Includes ambi safety and ambi mag catch for modern control and left-hand friendliness
Mil-spec trigger for proven reliability and consistency
ZEROED black grip and quality small parts for a complete, cohesive build
Backed by CMMG’s reputation for innovation and dependable AR components
If you want to build or upgrade an AR lower with ambidextrous controls, solid mil-spec reliability, and clean modern styling, the CMMG S5CA642 ZEROED Lower Parts Kit Black Grip, Ambi Safety & Mag Catch, Mil-Spec Trigger, Fits AR-Platform/Mk4 (55CA642, 810097502307) is an outstanding foundation for your next rifle project.
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