NEW M4-76 Upper, M76 M-LOK Rail w/ Steel Nut, CUSTOMIZABLE, Pick your barrel length

Now: $824.76
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(3 reviews) Write a Review
Custom Uppers Ship in 2-6 weeks


M4-76 Upper

6 Available Lengths from 8" to 16.75"

Steel Barrel Nut

Wedge Lock Design

Includes a STEEL 4041 QD Socket

At Sons of Liberty Gun Works we believe in Quality Mil-Spec or better parts. We believe there is no substitute for quality and that your gun should be built right the first time, ready for hard use right out of the box. We believe a quality Bolt Carrier Group and a quality, accurate and long lasting barrel are the heart of a Combat Grade weapon. We believe in properly tuned weapons using the correct gas system length and quality buffer system components such as the Vltor A5 system and Sprinco Tactical Buffer Springs. We believe in our products and we back them up with a lifetime warranty. Our weapons our meant to be used hard and go in harm’s way, they won’t let you down.

The M4-76 is our newest rail design. It is built with all high quality components including a Steel Barrel Nut. At Sons of Liberty Gun Works we always tell our 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-SL. We have built our guns to run through years of hard use, and we have nothing to hide.

Bolt Carrier Group: Sons of Liberty Gun Works Bolt Carrier Group HPT/MPI
Bolt: precision machined from Carpenter Technology No. 158 alloy, heat treated per mil-spec, shot peened per ASTM B851/SAE AMS2430S, vibratory tumbled, individual high pressure/proof test fired (HPT), individual magnetic particle inspection ASTM E1444/E1444M (MPI), markings deep laser engraved (SP=Shot Peened/HPT=High Pressure Tested, MPI=Magnetic Particle Inspection.
Extractor: precision machined from 4340 tool steel alloy per SAE AMS6415T/AMS6484D (vs typical 4140; mil-spec allows for either 4140 or 4340), heat treat, shot peen per ASTM B851/SAE AMS2430S.
Extractor Retaining Pin: precision machined and ground S7 Tool Steel, heat treated per ASTM A681-08, shot peened per mil-spec print, manganese phosphate
Extractor Spring (premium spring eliminates need for Crane O-Ring), Tactical Springs/Sprinco 5 coil, ASTM Grade A401 Chrome Silicon wire stock, heat treated, stress relieved, Molybdenum-Disulfide infused, cryogenic processed (all post winding), mil-spec black insert/synthetic elastomer extractor buffer (nitrile-butadiene, shore hardness 80+/-5 durometer per MIL-PRF-6855)
Ejector: S7 Tool Steel, heat treated per ASTM A681-08, shot peened per mil-spec print, manganese phosphate
Ejector Spring, Tactical Springs/Sprinco ASTM Grade A401 Chrome Silicon wire stock, heat treated, stress relieved, Molybdenum-Disulfide infused, cryogenic processed (all post winding)
Gas Rings: mil standard stainless steel X3
Carrier: machined from AISI 8620 aircraft qualty alloy per ASTM A108/A322-13, full auto profile, heat treated (carburized/strain relieved per mil-spec print), hard chrome bore, precision ground gas key interface, Sons of Liberty Battle Flag logo deep laser engraved, manganese phosphate
Gas Key: machined from 4130 chromoly steel alloy per ASTM A108/A322-13, heat treated, hard chrome internal, manganese phosphate, Permatex sealed, Grade 8 Torx Plus cap screws torqued and staked all per mil-spec
Cam Pin: precision machined 4340 chromoly steel alloy per SAE AMS6415T/AMS6484D, heat treated/processed per mil-spec, manganese phosphate, solid film lubricant applied and cured per mil-spec
Firing Pin: precision machined 8640 steel alloy, heat treated/processed per mil-spec, hard chrome plate
Firing Pin Retaining Pin: precision machined from 1038 carbon steel, heat treated/processed per mil-spec, manganese phosphate

Barrel: Sons of Liberty Gun Works 16” 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
Weight: 19 Ounces
Barrel Finish: QPQ Corrosion Resistant Finish
Barrel Extension: QPQ coated M4 Feed Ramp Extension
High Pressure (proof) Tested (HPT)
Magnetic Particle Inspected (MPI)

Upper Receiver:
Material: Made from Mil-Spec 7075-T6 aluminum Cerra Forge forgings.
Exterior Finish: Anodized to Mil-Spec MIL-A-8625F, Type III, Class 2, Hard Anodic Coating, Flat Black Dye, Non-Reflective, NiAc Seal
Interior Finish: Dry Film Lube
T-Marks: Engraved T-Marks

Charging Handle: None

Gas Block: Sons of Liberty Lo-Pro Gas block made from 4140 Steel and Nitride Treated

Gas Tube: Sons of Liberty Melonited Stainless Steel

Rail System: SOLGW M76 Wedge Lock Rail

M-LOK Attachments

Steel Barrel Nut

Muzzle Device: Mil-Spec A2 Flash Hider

Sights: Front and Rear MBUS

Includes: Steel 41140 QD Socket M-LOK

Additional Details


3 Reviews

  • 5

    Published by Michael M on Mar 24th 2020

    excellent product! i bought the 13" rail with 13.7" barrel, nox, carpenter BCG and a radial SL charging handle. i first saw this rifle and company from a youtube channel by the name of Garand Thumb who reviewed this rifle. i had been searching for a while and could not decide on what to get until i saw the video. i live in Commifornia.... uh oops sorry California where you cannot really buy a complete rifle, so i bought this upper to go on a Aero lower(since the is the "firearm") with the BCM enhanced lower parts group, the Vltor A5 bundle through SOLGW and a B5 stock. i could not be happier with my purchase, the rifle is awesome and feels great, mind you i do not have a huge amount of experience with different products, but i can tell great craftsmanship went into this rifle and i cannot wait to shoot it more. thank you for your service to provide us citizens with great blasters!!! also purchased this during black friday and got a killer deal.

  • 4
    M4-76 Upper and M-LOK Rail

    Published by James Martinez-Ruiz on Feb 27th 2020

    Excellent upper! I ordered a 13.7" barrel with a 13" rail. The craftsmanship and pin and weld was second to none. My only complaint was the shipping dept doing a poor job packing the upper. Got some dents, but this is a tool. Did not contact SOLGW in regards the shipping incident. Great company and customer service!

  • 5
    5 stars all around

    Published by Haris Tareen on Nov 22nd 2019

    Great turn around time! Amazing No BS rail with great mounting options and feels amazing and well balanced. I will probably end up getting another one fairly soon!

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