CMMG ZEROED Adjustable Gas Block .750" Nitride 4140 Steel - 55DA31F

CMMG 55DA31F Zeroed Adjustable Gas Block - .750", Nitride 4140 Steel - 55DA31F - 810148627591

Product Description

Fine-tuning an AR-15 or AR-10 gas system often presents severe cycling challenges, such as over-gassing, excessive bolt speed, violent felt recoil, and increased backpressure when running suppressors. Standard non-adjustable low-profile gas blocks force fixed gas volume through the gas port regardless of ammunition pressure or suppressor backpressure, leading to brass deformation, premature internal component wear, and harsh recoil impulses. The CMMG ZEROED Adjustable Gas Block for .750" journals (55DA31F) resolves these gas management and cycling velocity limitations by delivering precise, micro-detent adjustment control inside a compact 4140 steel body.

Precision CNC-machined from 4140 steel and finished in a slick, heat-resistant Black Nitride coating, the ZEROED adjustable gas block features an intuitive click-detent adjustment mechanism. This allows shooters to meter gas flow from fully open down to restrictive levels, optimizing dwell time for specific projectile weights, subsonic loads, or high-backpressure suppressor staging. The click-detent design locks your custom gas setting securely in place, preventing setting drift under high heat, rapid firing, and extreme vibration.

Engineered to fit standard .750" diameter gas block journals, the low-profile footprint of the CMMG 55DA31F slides easily under modern slimline M-LOK or KeyMod handguards. Secured via robust dual set screws, it provides duty-grade gas metering, reduced felt recoil, and ultimate reliability for suppressed carbines and precision competition rifles.

*Armorer Bench Notes & Real-World Staging Guidance:

Fitment & Journal Compatibility Matrix: Fits barrel gas block journals with a standard .750" outer diameter (e.g., standard carbine, mid-length, or rifle-length AR-15 and AR-10 barrel profiles). Compatible with standard carbine, mid, or rifle gas tubes using a standard gas tube roll pin.

Installation & Gas Tuning Sequence:

1. Safety check the firearm, remove the magazine, lock the bolt rearward, and physically and visually inspect the chamber to confirm a clear weapon.
2. Install your gas tube into the CMMG ZEROED gas block socket and secure it with the included roll pin.
3. Slide the gas block onto the .750" barrel journal, aligning the internal gas port precisely with the barrel's gas port hole.
4. Apply non-permanent blue threadlocker (Loctite 242 or Rocksett) to the bottom set screws and torque securely (typically 25–30 in-lbs) to knurled dimples on the barrel.
5. To tune: Start with the adjustment screw turned in to restrict gas, load one round into a magazine, and fire. Open the adjustment screw in single-click increments until the bolt locks rearward on an empty magazine, then add 1 to 2 additional clicks for operational reliability margin under adverse conditions.

Key Features

• Precision Micro-Click Detent Adjustment: Fine-tunes gas flow to optimize cycling for suppressed, unsuppressed, subsonic, and high-pressure ammo.
• 4140 Steel Construction: Heavy-duty steel body withstands intense thermal exposure, erosion, and high cyclic gas pressures.
• Black Nitride (QPQ) Protective Finish: Guards internal and external surfaces against carbon buildup, corrosion, and severe heat cycling.
• Low-Profile Design: Compact dimensions fit easily under most slim free-float M-LOK, KeyMod, and Picatinny handguards.
• Standard .750" Barrel Fitment: Compatible with the majority of standard AR-15 and AR-10 barrel gas block journals.
• Secure Dual Set Screw Attachment: Locks firmly onto barrel dimples to eliminate gas block walk during sustained firing schedules.

Product Specifications

• Brand: CMMG
• Series: ZEROED
• Model: Adjustable Gas Block - .750"
• MPN: 55DA31F
• UPC: 810148627591
• Journal Diameter: .750"
• Adjustment Type: Click-Detent Adjustable
• Attachment Method: Dual Set Screws
• Material: 4140 Steel
• Finish / Color: Black Nitride