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CMMG Mk4 5.7X28mm Resolute Upper Group Receiver Up to 14% Off w/ Free Shipping — 6 models

CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Tungsten, 57B40E4-TNG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Midnight Bronze, 57B40E4-MB
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Sniper Grey, 57B40E4-SG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Charcoal Green, 57B40E4-CG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Coyote Tan, 57B40E4-CT
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Titanium, 57B40E4-TI
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Tungsten, 57B40E4-TNG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Midnight Bronze, 57B40E4-MB
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Sniper Grey, 57B40E4-SG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Charcoal Green, 57B40E4-CG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Coyote Tan, 57B40E4-CT
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Titanium, 57B40E4-TI
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Tungsten, 57B40E4-TNG
1 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Tungsten, 57B40E4-TNG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Midnight Bronze, 57B40E4-MB
2 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Midnight Bronze, 57B40E4-MB
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Sniper Grey, 57B40E4-SG
3 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Sniper Grey, 57B40E4-SG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Charcoal Green, 57B40E4-CG
4 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Charcoal Green, 57B40E4-CG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Coyote Tan, 57B40E4-CT
5 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Coyote Tan, 57B40E4-CT
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Titanium, 57B40E4-TI
6 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Titanium, 57B40E4-TI
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Tungsten, 57B40E4-TNG
7 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Tungsten, 57B40E4-TNG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Midnight Bronze, 57B40E4-MB
8 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Midnight Bronze, 57B40E4-MB
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Sniper Grey, 57B40E4-SG
9 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Sniper Grey, 57B40E4-SG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Charcoal Green, 57B40E4-CG
10 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Charcoal Green, 57B40E4-CG
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Coyote Tan, 57B40E4-CT
11 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Coyote Tan, 57B40E4-CT
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Titanium, 57B40E4-TI
12 of 12 images
CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Titanium, 57B40E4-TI

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Questions & Answers
Will this upper work on a mil spec lower reciever ?

Yes it is a mk4 so you’ll need the cmmg 5.7x28 AR compatible magazines

by Juice, Verified Owner, January 5, 2025
Does this come with a BCG? Expert Answer

Yes, the CMMG Mk4 5.7X28mm Resolute Upper Group Receiver will include a BCG and charging handle.

by Ethan, Gear Expert, May 1, 2023
View All Q&A You Have a Question? Ask!
Customer Reviews
Most Recent Reviews
Sweet upper as always by CMMG by First-Timer, Verified Owner, May 4, 2024
This is a very sweet upper as always by CMMG. The craftsmanship and finish is amazing. Plan to send rounds down range this weekend! Can not go wrong with CMMG.
0/1 found this helpful
Most Recent Reviews
Cmmg Mk4 5.7x28mm Resolute upper group receiver by Ralph, Verified Owner, May 20, 2023
Just received my 5.7x28 upper. Fit perfect on my lower. Functioned flawlessly, After 200 rounds no fail to feed no jams functioned great. Looks great All of my buddies are jealous and are thinking about ordering one for themselves. A littl...
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Read All 2 Reviews
6 Models Available
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ATTENTION! We currently do not ship this product to P.O. Boxes, AK, CA, CT, DE, HI, MA, NJ, NY, U.S. Territories, or select Colorado locations. Please see our policies for more information or a detailed list of locations.

Product Info for CMMG Mk4 5.7X28mm Resolute Upper Group Receiver

Personal defense calibers like 5.7x28mm have become a big thing in the last few years, and if youre looking for PDW ballistics and the classic style and balance of a carbine then youre in luck. Combine this RESOLUTE Upper Group with either our Mk57 Lower or a standard AR15 lower group and CMMGs 5.7 AR Conversion Magazines and youll be ready to hit the range!image

WARNING: California`s Proposition 65

Specifications for CMMG Mk4 5.7X28mm Resolute Upper Group Receiver:

Manufacturer: CMMG
Caliber: 5.7x28mm
Overall Length: 25.3 in
Barrel Length: 16.1 in
Barrel Profile: Medium Tapered
Barrel Twist Rate: 1-9
Muzzle Device: CMMG Zeroed Muzzle Brake
Fabric/Material: 6061-T6 Aluminum
Gun Rail: M-LOK
Gun Make: CMMG
Gun Model: CMMG Mk4
Weight: 4 lb
Magazine Included: No
Mount Type: M-LOK

Package Contents:

  • CMMG Mk4 5.7X28mm Resolute Upper Group Receiver

What firearm models does the manufacturer say CMMG Mk4 5.7X28mm Resolute Upper Group Receiver is compatible with?

The manufacturer suggests that CMMG Mk4 5.7X28mm Resolute Upper Group Receiver is compatible with CMMG Mk4

CMMG Mk4 5.7X28mm Resolute Upper Group Receiver Orderable Models

List of Orderable Models

  • CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Tungsten, 57B40E4-TNG , MPN: 57B40E4-TNG , UPC: 810097504370 , Code: 2CM-URC-CP49-57B40E4-TNG
  • CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Midnight Bronze, 57B40E4-MB , MPN: 57B40E4-MB , UPC: 810097504349 , Code: 2CM-URC-CP49-57B40E4-MB
  • CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Sniper Grey, 57B40E4-SG , MPN: 57B40E4-SG , UPC: 810097504356 , Code: 2CM-URC-CP49-57B40E4-SG
  • CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Charcoal Green, 57B40E4-CG , MPN: 57B40E4-CG , UPC: 810097504325 , Code: 2CM-URC-CP49-57B40E4-CG
  • CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Coyote Tan, 57B40E4-CT , MPN: 57B40E4-CT , UPC: 810097504332 , Code: 2CM-URC-CP49-57B40E4-CT
  • CMMG Mk4 5.7X28mm Resolute Upper Group Receiver, 16.1in, Titanium, 57B40E4-TI , MPN: 57B40E4-TI , UPC: 810097504363 , Code: 2CM-URC-CP49-57B40E4-TI
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Last updated 2026-08-04 UTC.