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-SML is our entry level carbine build. It is built with all high quality components. 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)
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: Sons of Liberty Gun Works SOLO M-LOK Rail system.
Weight: 11.4 OZ
Inside Diameter: 1.3" ID
Finish: Mil-Spec Type III Class 2 Hard Coat Anodizing per Mil-Spec Mil-Spec MIL-A-8625F
Barrel Nut: 7075 Barrel nut w/ Hard Coat Anodizing
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
Muzzle Device: Mil-Spec A2 Flash Hider
Sights: Front and Rear MBUS