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Reviews & Ratings for CMMG Mk4/AR15 Upper Receiver Assembly — 11 reviews

(11 reviews)
CMMG Mk4/AR15 Upper Receiver Assembly
CMMG Mk4/AR15 Upper Receiver Assembly
As Low As $139.99 Save Up to $9.96
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Most Helpful Positive Review CMMG Mk4 Upper
This is an excellent upper receiver. Fit nice and snug on my lower receivers. Matches great with my Noveseke billet lower. Also, it matches perfectly with my SLR Helix handguard. The profile looks like they were built to match. If you have a handguard with anti rotation tabs, these may not work...
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Most Helpful Negative Review High quality, terrible specs
Bought one of these uppers for a build. Quality is top notch, worthy of 4-5 stars. We will see how the polymer brass deflector holds up. No forward assist plus the polymer makes this thing extremely light. Problems come though with how it is spec'd. This upper has a significantly thicker base than a...
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Not compatible with Midwest industries handguards

by Violated Virginian, Verified Owner from VA, United States Written on March 7, 2026
The upper is lightweight, the shell deflector and dust cover are plastic, no forward assist. I found out the Midwest industries handguard with tangs that go around the sides of the upper are not compatible due to the thickness of the upper, a trip to the machine shop with the handguard should fix this problem.
Pros:
  • Lightweight
Cons:
  • Not milspec
Best Used for:
  • Lightweight build
Would recommend: Yes
Was it helpful to you? Yes | No
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Nice upper

by jimmy, Verified Owner from AZ, United States Written on May 9, 2025
Very nice looking and functioning upper. Tight fit up and runs smooth. It’s been good to me so far
Would recommend: Yes
Was it helpful to you? Yes | No
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CMMG Upper is top notch

by Home, Verified Owner from TX, United States Written on April 24, 2025
First build with CMMG upper and Handguard. Very nice quality on machining and finishing. No fwd assist is nice! Nice and light for my 338 ARC setup.
Pros:
  • Hi quality
Cons:
  • None
Best Used for:
  • any ar15 build
Would recommend: Yes
Was it helpful to you? Yes | No
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Sniper Grey slick side upper

by Hoang, Verified Owner from NY, United States Written on March 21, 2025
Quality is amazing, matches my aero precision m4e1 lower in sniper grey.
Would recommend: Yes
1 of 1 found the following review helpful.
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cmmg mk4/ar15

by Alan Barry, Verified Owner from MO, United States Written on December 18, 2024
Fits great haven’t went to the range yet but I expect it to run well
Would recommend: Yes
0 of 1 found the following review helpful.
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Review of CMMG Mk4/AR15 Upper Receiver Assembly

by Tony, Verified Owner from TX, United States Written on May 4, 2024
This is the second CMMG upper I've purchased. The first one was for a Mk17 build. I was not impressed with the Cerakote finish. That'ssomething CMMG needs to do. I hoping the new was is better. I built a MKG glock Pistol with my new upper. I haven't taken it to the range yet, but I have no doubt it will perform well. I was very satisfied with my MK17. I've also used the upper with the 9mm Conversion kit/mags. I must say it's a most versatile upper.
Pros:
  • Extremely Versatile
Cons:
  • The Cerakote finish could be better
Best Used for:
  • N/A
Would recommend: Yes
1 of 1 found the following review helpful.
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great upper

by Anthony Gross, Verified Owner from KY, United States Written on March 14, 2024
Best looking slick side upper in my opinion. I have one on my 9mm and 300 blk. Great price and a quality part. Exactly what you would expect from cmmg. I really like that it ships with a dust cover so i dont have to buy one.
Would recommend: Yes
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Cmmg stripped upper receiver

by Pepe, from FL, United States Written on December 18, 2023
Just a very light beautifully finished upper reciver.
Pros:
  • very light and affordable
Cons:
  • None
Best Used for:
  • Any ar reolacement
Would recommend: Yes
Was it helpful to you? Yes | No
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Cmmg upper receiver MK4

by Gucci build, from NC, United States Written on January 24, 2023
I’m starting a build and decided to choose Cmmg because I already have a Cmmg lower. This lower is a perfect match with no wiggle and looks good with the tungsten grey lower. I’ll be doing a 5.56 10.5 so wish me luck.
Pros:
  • Perfect fit. Good price. Rear charging handle
Cons:
  • None
Would recommend: Yes
Was it helpful to you? Yes | No
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Last updated 2025-11-12 UTC.