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Questions & Answers
Will this upper also take .223 rounds?

yes, only out of 5.56 barrels can you do that. but not the opposite.

by shrek, Verified Owner, February 9, 2026
Caliber:
5.56x45mm NATO
Overall Length:
23.8 in
Barrel Length:
14.5 in
Gas System Length:
Carbine Length
Barrel Twist Rate:
1-7
Threads per Inch:
1/2x28
Handguard Type:
M-LOK ATLAS S-ONE
Muzzle Device:
CMMG ZEROED SVD Brake Pinned & Welded
Finish:
Matte
Color:
Black
Handguard Length:
13.5 in

Code: 2CM-URC-55B360BAB-55B360B-AB

MPN: 55B360B-AB

UPC: 810148621926

List: $609.95Save 15%
$519.99

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Product Info for CMMG Upper Group Resolute Mk4 5.56x45mm 14.5in P&W Upper Receiver

The CMMG Upper Group Resolute Mk4 5.56x45mm 14.5in P&W Upper Receiver was created to be the ideally suited item for anybody trying to find a high quality choice..image

Developed working with some of the very most robust and dependable components in existence, these AR15 Upper Receivers through CMMG can provide something that will give numerous years of dependability.

CMMG has been generating high quality products for a number of years, and the CMMG Upper Group Resolute Mk4 5.56x45mm 14.5in P&W Upper Receiver is their particular approach to demonstrating exactly how much they care.

At OpticsPlanet, we ensure that it is our obligation to get the best solution for all of your requirements, and featuring the CMMG Upper Group Resolute Mk4 5.56x45mm 14.5in P&W Upper Receiver is a thing that we are delighted to offer.

Specifications for CMMG Upper Group Resolute Mk4 5.56x45mm 14.5in P&W Upper Receiver:

Manufacturer: CMMG
Caliber: 5.56x45mm NATO
Overall Length: 23.8 in
Barrel Length: 14.5 in
Gas System Length: Carbine Length
Barrel Twist Rate: 1-7
Threads per Inch: 1/2x28
Handguard Type: M-LOK ATLAS S-ONE
Muzzle Device: CMMG ZEROED SVD Brake Pinned & Welded
Finish: Matte
Color: Black
Fabric/Material: Steel
Handguard Length: 13.5 in
Gun Make: AR Platform
Gun Model: AR-15
Weight: 4.1 lb
Bolt Carrier Group Included: No
Charging Handle Included: No

Package Contents:

  • CMMG Upper Group Resolute Mk4 5.56x45mm 14.5in P&W Upper Receiver

CMMG Upper Group Resolute Mk4 5.56x45mm 14.5in P&W Upper Receiver Orderable Models

List of Orderable Models

  • CMMG Upper Group Resolute Mk4 5.56x45mm 14.5in P&W Upper Receiver, No BCG or CH, AR-15, Black, 55B360B-AB , MPN: 55B360B-AB , UPC: 810148621926 , Code: 2CM-URC-55B360BAB-55B360B-AB
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