CMMG AR-15 MK4 Receiver End Plate – 55CA9DD (UPC 815835017433)
Lock down your buffer tube the right way with the CMMG AR-15 MK4 Receiver End Plate—a rugged, mil-spec–style component built for reliability, repeatability, and clean installs. Whether you’re refreshing a hard-run carbine or assembling a brand-new lower, this end plate provides the precise fit you expect from CMMG, delivering consistent alignment for your receiver extension while retaining the rear takedown pin detent spring exactly where it belongs.
Why This End Plate Belongs in Your Build
Mil-spec form factor for broad compatibility with AR-15/M4 pattern lowers and carbine receiver extensions.
Steel construction for long-term durability under recoil and repeated maintenance cycles.
Proper spring capture helps ensure the rear takedown pin detent spring stays seated during install and service.
Clean, low-profile design pairs with standard castle nuts and most aftermarket stocks without interference.
CMMG quality control backed by a brand trusted by armorers, competitors, and enthusiasts.
Purpose-Built for Rock-Solid Assembly
The end plate is a small part that does a critical job. The CMMG MK4 Receiver End Plate keeps your carbine receiver extension square and consistent as you torque the castle nut, supporting proper buffer system alignment and smooth cycling. Its precise geometry helps prevent rotation of the receiver extension over time—key for maintaining your stock orientation and protecting internal components.
Broad AR-15 Platform Compatibility
Designed around common AR-15 specs, this end plate is compatible with:
AR-15/M4 pattern lowers (MK4/standard AR).
Carbine-length receiver extensions (commonly called “buffer tubes”).
Standard castle nuts used in mil-spec style builds.
Note: Works with most mainstream parts. If you’re using proprietary receiver extensions or specialized sling plates, confirm interface dimensions before ordering.
Ideal Use Cases
New Builds: Complete your lower with a dependable, mil-spec–style end plate.
Refreshes & Repairs: Replace worn or marred plates during stock or buffer tube upgrades.
Duty & Training Carbines: Choose a robust component that holds up to high round counts and frequent maintenance.
Installation Tips (General Guidance)
Unload and clear your firearm before any work.
Ensure the rear takedown pin detent and spring are properly seated in the lower.
Slide the end plate over the receiver extension and align it with the lower receiver.
Thread the castle nut against the end plate and torque to spec per your armorer’s manual.
If required by your doctrine, stake the castle nut at one or two points to resist loosening over time.
Always follow current manufacturer specs and safe gunsmithing practices. If unsure, consult a qualified armorer.
Clean, No-Nonsense Aesthetics
The minimal profile pairs well with classic and modern builds alike. No extra protrusions means nothing to snag on gear and nothing to distract from your rifle’s lines—just the dependable function you need every time you shoulder the carbine.
Technical Details at a Glance
Product: CMMG AR-15 MK4 Receiver End Plate
Model/SKU: 55CA9DD
UPC: 815835017433
Platform: AR-15/M4 pattern (MK4/standard AR)
Material: Steel (mil-spec style)
Interface: Carbine receiver extension + standard castle nut
Orientation: Ambidextrous compatible (non-QD, low-profile plate)
SEO Quick Hits
CMMG AR-15 MK4 receiver end plate
AR-15 buffer tube end plate, mil-spec style
Compatible with carbine receiver extensions and castle nuts
Durable steel construction for AR-15/M4 builds
Model 55CA9DD, UPC 815835017433
The Bottom Line
For builders who value fit, function, and longevity, the CMMG AR-15 MK4 Receiver End Plate (55CA9DD) is a smart, straightforward choice. It’s the kind of part you install once, trust completely, and barely think about again—exactly how a foundation component should be.
The End
