BRN-4 416/MR556 COMPLETE BOLT CARRIER GROUP Reviews & Ratings

BRN-4 Complete Bolt Carrier Group for 416 Type Firearms This Completely assembled BRN-4 Bolt Carrier Group is ready to drop into HK® 416, MR556 or other compatible upper receivers & firearms. Utilizing high quality materials, finishes and inspection criteria, this BCG provides great value as a replacement or build component. The Brownells BRN-4 bolt is machined from high performance 9310 steel, heat treated, magnetic particle inspected for defects and finished in Black Nitride. The Black Nitride finish combined with the piston operating system makes for extremely simple cleanup. BRN-4 Bolt Carrier Group is designed to be compatible with standard AR-15 or M16 type triggers. Common AR-15 aftermarket drop-in, cassette or mil-spec type triggers will work with the BRN-4 BCG. The nitride finished, 8620 forged tool steel carrier operates smoothly in the upper, thanks to the high lubricity of the nitride finish. The integrated piston key removes any concern of staked gas keys working loose and makes for an extremely strong carrier. Also, by forging the carrier instead of machining from bar stock, the carrier has an extremely strong internal material structure. Includes Bolt with Extractor & Ejector assembly, Carrier (M16 type), Cam Pin, Firing Pin, Firing Pin Spring, Firing Pin Retainer. Carrier is compatible with 416 Type Firearms as well as MR556 Firearms (both military/LE & commercially available Heckler & Koch® Firearms).

See all of our AR15s and AR15 parts here.

View Product

Write a review

4 Stars

2 Stars

Reviews Summary

The BRN-4 BCG has garnered mixed feedback. Many users are satisfied with its quality and performance, noting it as a good alternative to expensive OEM parts. However, some customers reported manufacturing inconsistencies and dimensional errors, which raised concerns about compatibility. Overall, it appears to be well-made, but with some quality control issues to address.

What Reviewers Are Saying

Product Quality

70%

Reviewers broadly acknowledge the quality of the BRN-4 BCG, often noting it as a great alternative to high-cost OEM parts. However, inconsistencies in manufacturing have raised concerns about its reliability and compatibility with genuine HK components.

Compatibility Issues

40%

Several customers reported problems with dimensional specifications leading to compatibility issues with HK parts. This has been a recurring concern, with mentions of potential damage to original components if used as-is.

Performance

50%

While many reviewers noted satisfactory performance and consistent functioning in their builds, some highlighted issues like metal chips from the firing pin spring after use. These discrepancies indicate a need for attention to certain components.

Pricing and Value

60%

A common sentiment reflects appreciation for the product's pricing, with users noting it offers good value compared to often difficult-to-obtain factory HK parts, thus making it an economical choice.

Manufacturing Variability

50%

The reviews indicate some inconsistencies in manufacturing quality, with complaints ranging from hardening issues to dimensional errors, suggesting a need for improved quality control measures.

Sort by Filter by rating

Out of spec parts

This part was out of spec and wouldn't match my HK piThis part was out of spec and wouldn't match my HK piston This part was out of spec and wouldn't match my HK piston height. It would have damaged my original parts if I had used it. There's several threads on the hk forums about the same issues and they have not resolved any of this in more than a year.height. It would have damaged my original parts if I had used it. There's several threads on the hk forums about the same issues and they have not resolved any of this in more than a year.

by GERMAN F. on August 06, 2024

Verified Purchase

Was this review helpful? 2

Still same issues as previous batches

Hardening issues as well as dimensional manufacturing errors made this unusable with my genuine HK parts.