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AR-15/M16 M4 Receiver Castle Nut
AR-15/M16 M4 Receiver Castle Nut
AR-15/M16 M4 Receiver Castle Nut
AR-15/M16 M4 Receiver Castle Nut
None
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ERGO GRIPS - AR-15/M16 M4 Receiver Castle Nut

9 Reviews
AR-15/M16 M4 Receiver Castle Nut
Brownells #
573000064
MFR #
4971
UPC
874748005333
$9.29
Coupon Code
Purchase Limit Help

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Specifications
Color:
Black
Material:
Steel
Make Model Fit:
AR-15.Universal;AR-308.Universal
Restriction
Gun Part Restrictions:
Yes
Prop 65 restriction:
WARNING: This product could expose you to chemicals including cadmium, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65 Warnings.ca.gov
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International purchase information

What is the ERGO GRIPS - AR-15/M16 M4 Receiver Castle Nut?

Falcon Industries/ERGO brings this receiver extension castle nut for M4 style receiver extension tubes.

See all of our AR15s and AR15 parts here.

Gun Part Restriction
Gun Parts have restricted shipping to CA.

Prop 65WARNING: Cancer & Reproductive Harm - www.P65Warnings.ca.gov

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AR-15 RECEIVER EXTENSION CASTLE NUT REVIEWS

4.1
9 Reviews
5 Stars
78%
4 Stars
0%
3 Stars
0%
2 Stars
0%
1 Stars
22%
Reviews Summary
Overall, customers are satisfied with the AR-15 Receiver Extension Castle Nut, appreciating its solid construction and fit. However, a few users faced issues with deformation at high torque and some noted it didn't fit their specific setups perfectly. Mostly, it meets the basic functional requirements effectively.
What Reviewers Are Saying
Product Quality
65%
A majority of reviewers appreciate the solid metal construction and effective functionality of the castle nut. The quality meets expectations with several noting adequate fit and finish, contributing to positive experiences.
Compatibility
30%
Compatibility issues were highlighted by several users, with some experiencing fits that were either too tight or out of spec with their setups. While some found it worked perfectly, this inconsistency led to varied user experiences.
Performance Under Pressure
20%
Some customers reported issues with the castle nut deforming when subjected to high torque settings. This suggests potential concerns regarding the metal's durability under stress, impacting its performance.
Value for Money
50%
Reviewers consider the pricing to be fair compared to its functionality, with several emphasizing that it balances quality and affordability well, making it a solid choice for both budget builds and standard installations.
Fit and Finish
40%
Most reviewers commented positively on the dimensions and finishes, with some specifically noting the standard mil-spec finish and correct dimensions that align with usage in typical military setups.
5
High quality products
Fast shipping
by Thomas Hobbs on June 30, 2026
Verified Purchase
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5
Solid Nut!
Does the job & does it well! My UTG wrench didnt pop off with appropriate pressure. Solid metal construction & the light grease coating helped it go on perfect! No complaints here!
by Tom on January 26, 2021
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5
Worked good for me
Got this to use on a Remington 870 with a stock adaptor. It went together well and appears to be within spec. The fit & finish are adequate and it did what its supposed to.
by Joe on May 11, 2020
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5
It works
This works. It fit the wrench better than some castle nuts I've used in the past. I was hesitant purchasing such a part from Ergo but it's perfect. Simple, not the most or least expensive (not cheap either) but it just works.
by Sandman on April 25, 2020
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5
Good product
Used this for a budget build and worked great! No problems at all.
by Jeff on September 23, 2019
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View All 9 Reviews
Customer Questions
0 Questions