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Sons of Liberty Gun Works M4-89 5.56 AR-15 Rifle - 13.7" (Pinned)

AR-15 Rifle

Out of stock

FFL Required Before Shipping.
Please have your dealer email a copy of their FFL to [email protected] or fax it to 253-218-2998, referencing your name and order number.


The M4-89 is Sons of Liberty's premier fighting rifle, featuring a 13.7″ combat grade barrel, Pin and Welded Nox Muzzle Device, A5 buffer system, Liberty Fighting Trigger, and B5 furniture. At Sons of Liberty Gun Works they always tell their customers, its not what a rifle company tells you, it’s what they don’t tell you. Below you will find the complete specifications on the M4-89. They have built their guns to run through years of hard use, and they have nothing to hide.


Upper Features & Specifications:

  • Material: Made from Mil-Spec 7075-T6 aluminum Cerra Forge forgings.
  • Finish: Anodized to Mil-Spec MIL-A-8625F, Type III, Class 2, Hard Anodic Coating,
  • Flat Black Dye, Non-Reflective, NiAc Seal
  • T-Marks: Engraved T-Marks
  • Charging Handle: Liberty Charging Handle
  • Gas Block: Sons of Liberty Lo-Pro Gas block made from 4140 Steel and Nitride Treated with Knurled Head Set Screws
  • Gas Tube: Sons of Liberty Mid Length Melonited Stainless Steel


Lower Receiver Features & Specifications:

  • Lower Receiver: Sons of Liberty Gun Works Forged Lower Receiver
  • Material: Made from Mil-Spec 7075-T6 aluminum Cerra Forge forgings
  • Finish: Anodized to Mil-Spec MIL-A-8625F, Type III, Class 2, Hard Anodic Coating, Flat Black Dye, Non-Reflective, NiAc Seal Contour is fully machined leaving no flash marks from the forging.
  • Hidden lowers are cut with M16 auto pocket.
  • Safe, Fire, and Full Auto Pictograms.
  • Various Roll Marks


Buffer Features & Specifications:

  • Buffer System: Enhanced A5 Buffer System
  • Receiver Extension: 9 Position Loyal 9 Receiver Extension Tube made from 7075-T6 Aluminum
  • Buffer: A5H2 Buffer
  • Buffer Spring: Sprinco Green Spring


Handguard Features & Specifications:

  • Rail System: 13″ Sons of Liberty Gun Works M89 Drive Lock Rail system.
  • Inside Diameter: 1.4″ ID
  • Finish: Mil-Spec Type III Class 2 Hard Coat Anodizing per Mil-Spec Mil-Spec MIL-A-8625F
  • Barrel Nut: Steel
  • Free Floating Design
  • Grade 8 Fasteners
  • Anti Rotation- Anti Slip Design
  • No Special Tools Need for Barrel Nut
  • Continuous top rail design
  • Mil-Spec 1913 Mounting rails


Barrel Features & Specifications:

  • Barrel: Sons of Liberty Gun Works 13.7” 4150CoMOV 1:7 MPI HPT Barrel
  • Caliber: 5.56 NATO Chamber
  • Barrel Steel: 4150 CrMoV (Chrome Moly Vanadium per MIL-B-11595E)
  • Twist Rate: 1/7 Twist Six Groove
  • Thread Pitch: 1/2-28 Threaded Muzzle
  • Gas Block: .750″ Gas Block Journal with appropriately sized gas port
  • Barrel Finish: QPQ Corrosion Resistant Finish
  • Barrel Extension: QPQ coated M4 Feed Ramp Extension
  • High Pressure (proof) Tested (HPT)
  • Magnetic Particle Inspected (MPI)
  • Muzzle Device: NOX Keymo Muzzle Device


Other Parts:

  • Receiver end plate: Quick Detach End Plate with properly staked Forwards Controls Design Castle Nut
  • Fire Control Group: Liberty Fighting Trigger 6- 6.5lb
  • Grip: B5 P23 Grip
  • Stock: B5 Bravo Stock Black
  • Sights: None, Optics Ready



  • Tactical Soft Case
  • (3) SOLGW Steel 30rd Mags
  • 2oz Bottle of S.P.E.C. 76 Lubricant
  • SOLGW Sticker & Patch
  • LIFETIME Warranty Certificate
More Information
SKU M4-89-13.7
Product Type AR-15 Rifle
Manufacturer Sons of Liberty Gun Works
Gas Block Diameter .750"
Thread Pitch 1/2x28
Twist Rate 1:7
Inside Diameter 1.4"
Color Black
Rail Length 13"
Finish Anodize
Barrel Length 13.7"
Caliber 5.56 NATO
Threaded Yes
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