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Atlas Custom Works WA M4 GBB Series CNC Aluminum Bolt Carrier

[37534 / ACW-GB132]
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The Atlas Custom Works WA M4 GBB Series CNC Aluminum Bolt Carrier is an upgraded bolt carrier group. The Aluminum Bolt Carrier improves the durability and performance of your WA M4 by improving gas flow.

Manufacturer: Atlas Custom Works
Model: WA M4 GBB Series CNC Aluminum Bolt Carrier
Package Includes: Bolt Carrier
Warranty Length: 45 Days
Warranty Handler: Airsoft GI (Warranty Policy)


  • Aluminum Alloy Construction
  • Compatible w/ the Western Arms GBBR Series
  • OEM Replacement

Please Note:

  • Professional installation is recommended. Improper use or installation of upgrade parts are 99% of the time the cause of failures of these items.
  • Please thoroughly inspect any parts for defects before attempting installation. Due to the high possibility of damage from improper installation, we will not warranty parts after attempting installation.

Manufacturer: Atlas Custom Works
see 1 reviews | Write a Review
verified buyer
B. CHANG | 2019-11-19
Product Information:
I'm using this carrier with a stock G&P Negative Pressure Nozzle which after some minor fitment issues works without issue.

Due to the nature of aftermarket parts and differences in manufacturing, some tolerances may be tighter or looser than original parts.

In this case, the tolerance on the sides of the wide block section located near the front on top where the nozzle meets the carrier are ~1-2mm too wide and need to be worn* in or filed slightly for smoother cycling and return of the nozzle to the carrier.

As for the performance, this carrier is nearly 1/3 the weight of the stock carrier which increases the system's cyclic rate. This helps increase gas efficiency and save you money while boosting performance. The paint does wear after 300-500 bbs, but after ~1000-1500 bbs there is still no significant metal deformation on areas that see direct metal-on-metal contact such as the lip the bolt catch touches and the bottom of carrier where the roller hammer touches.

Aside from paint wear, this carrier is still going strong and works great in full auto.

Mass of Atlas Custom Works Carrier w/o Nozzle:
2.3 ounces | 66 grams

Mass of Stock G&P Carrier w/o Nozzle:
5.4 ounces | 150 grams

-Lightweight (~1/3 weight of stock G&P Carrier)

-Fast and Snappy Bolt Cycle

-Less felt recoil using stock buffer/spring combo. (could be pro or con)

-Gas Efficient (Helps with full auto)

-Built-In Nozzle Retaining Lock Relief Cuts for easy removal.

-Less felt recoil using stock buffer/spring combo. (Could be pro or con)

-Requires Fitment if not using the Atlas Customs nozzle

-Slightly offspec in overall length of carrier by ~1mm and nozzle fitment into carrier by ~1-2mm.

-Diameter of the hole where the valve on the back of the nozzle goes through is very tight fit and off-center from nozzle by ~0.25-0.5mm (Annoying to assemble, doesn't adversely affect blow-back action or FPS)

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