Gun Review: Sons of Liberty M4-SML


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A properly built AR-15-style rifle can be built to suit a wide range of tasks, from hunting to plinking to self-defense. With just a few tools, a little money and YouTube, an enthusiast can assemble their very own bespoke Modern Sporting Rifle. In fact, a lot of companies selling complete ARs do the same thing (minus the YouTube time). San Antonio’s Sons of Liberty Gun Works is one of them. That’s a good thing, not a bad thing . . .

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The gun tested here is the Sons of Liberty Gun Works’ M4-SML. It’s one of their most basic and most popular firearms, MSRP’ing for $1575. Given that this is a “parts gun,” TTAG readers who roll their own (and may roll their eyes) — and those who want a rifle that’s ready-to-go straight out of the box — probably want to know exactly what they get for their money. If so, skip to the detailed specifications below.

There are two main reasons to buy a Sons of Liberty Gun Works M4-SML, rather than building something similar/identical in your garage. First, buying the complete gun saves you time (which equals money). Second, it saves you from making mistakes during assembly (which equals frustration).

While you may argue with some of the choices below, Sons of Liberty chooses these parts based on thousands of hours of testing and decades of gun building experience. They inspect and assemble precision parts with precision, test them separately, test them together, stick the rifle in a box and send it to gun stores. The main advantage is the one that Sons of Liberty sets as its goal: reliability.

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This is not my first Sons of Liberty rifle testing rodeo. I’ve fired thousands of rounds through one of their full auto SBRs (short-barred rifle) without any maintenance (the rifle that is). In all, the gun ate some 14k rounds without a sniff of Hoppe’s. (It’s Frog-Lubed up regularly, but that’s it.) No malfunctions. That’s far beyond a mil-spec AR’s normal service life.

To achieve that kind of reliability, Sons of Liberty turn their back on DIY AR gizmos and gimmicks, focusing on relatively simple parts that deliver optimal function over a long time period. They strive to anticipate the common points of failure under extreme conditions and preemptively reinforce those components to push beyond normal service life. How well? “Sons of Liberty Gun Works will stand behind this weapon and repair any defects free of charge so long as the Barrel, Receivers, Bolt Carrier Group and Buffer system remain in the original configuration.”

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Our test gun came with flip-up iron sights and a Vortex Viper 1-4 power scope. Oddly enough, I have this scope on a couple of my guns and think highly of the entire line. The gun is basic. There’s no ambidextrous magazine release, bolt release or off set sights. No barrel fluting or special paint scheme. The M4-SML has the look and feel of my Army-issue M4, with a different hand guard and a much, much better trigger.

[Note: the M4-SML is a direct impingement rifle, which I do not prefer. In fact, I’ll never buy anything other than a piston driven AR, as long as the caliber allows it. But that has nothing to do with the rifle’s performance.]

Although this M4-SML is basic, it reminds me of how much I like the basics, and how great basic really is when someone gets it right. The 16″ version balanced well and easy, quick to swing and stop. The hand guard diameter is fairly small — I can wrap my hand all the way around it and touch my ring finger to my thumb — but it flairs out at the end to accommodate the Keymod rails. That balance makes a 16″ barrel gun swing like a 14″.

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I put a total of 560 rounds through the M4-SML. The first 500 were straight through. I lubed up the gun before I fired it, spraying the bolt, breach and barrel with RemOil, and started shooting. Using PMags, a few different steel magazines and a Surfire 60-round magazine, I poured rounds out of this thing.

I shot mostly kneeling and walking, but I also recreated a few of my TIC (Troops in Contact) ballistic experiences, shooting off the hood of my truck and shooting under my truck with the receiver flat on the ground. I shot the M4-SML in the dirt, between brush, got it dirty, and got it wet. I had zero malfunctions of any kind with any round in any magazine in any position. During my entire test cycle, I never cleaned the gun or lubed the M4-SML up again. No issues at all.

But what about accuracy? I tested the 55gr, 62 grain, and 64 grain rounds, firing 60 rounds total for accuracy off of bags at 100 yards. The results were boringly consistent. Nothing shot better than 1″ five shot groups, but nothing shot worse than 1.1″ either. To be clear, I shot these a day after the reliability test, without lubing or cleaning the gun in any way. MOA groups with zero cleaning at this stage is very, very good.

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Most people building their own AR from scratch aren’t going to get these results. Sons of Liberty makes it happen by paying attention to the little stuff, and knowing what they are doing. I’d trust this or any other Sons of Liberty rifle with my life, any day of the week. It shoots reliably, and it’s accurate well out past the round’s realistic performance range. If you want a basic AR that runs right, without gimmicks and hype, the M4-SML is an excellent choice

SPECIFICATIONS:

Caliber: .223
Weight: 7lbs 1oz
Price: $1575 msrp.

Barrel: 16″ 4150 Chrome Moly Vanadium per MIL-B-11595E, 1 in 7  six groove twist, magnetic particle inspected, high pressure tested, 1/2-28 thread pitch muzzle, QPQ Corrosion resistant finish on barrel and feed ramp extension,  .750″ gas block journal with appropriately sized gas port, weighting 27 ounces.  A2 flash hider.
Lower Receiver: Cerra Forge forgings Mil-Spec 7075-T6 anodized aluminum. Cut with M16 full auto pocket, with safe, fire, and full auto pictograms, and Angry Patriot roll marked.
Upper Receiver: Cerra Forge forgings from Mil-Spec 7075-T6 anodized aluminum. Dry film lube interior finish.Gas block is 4140 steel and nitride treated, gas tube is standard mid length stainless steel. Keymod rail, 13.9oz, inside diameter 1.3″, Mil-Spec type III Class 2 hard coat anodizing per MIL-A-8625F, free float design, no special tools needed for 7075 barrel nut w/hard coat anodizing. Continuous Mil-Spec 1913 top rail and mounting rails. Geisselle SSA fire control group
Furniture: MAGPUL MOE grip, B5 Polymer trigger guard, B5 Systems SOPMOD Bravo Stock

RATINGS (out of five stars): 

Appearance * * *
This is a basic, no frills forged AR. It doesn’t try to be anything else. Looks are highly subjective, and for a higher rating it would need something different aesthetically. As it is, it is dead on average.

Reliability * * * * *
On what counts, rounds downrange, over and over and over again, the Sons of Liberty M4-SML is the epitome of reliable.

Accuracy * * * *
An MOA gun is great and it’s hard to reliably get better than that. A few companies do it, usually at a higher cost with a heavier gun.

Customization * * * * *
It’s an AR with no specialized parts. You can change everything on this gun and change it back 10 times by yourself. But beyond maybe adding a silencer, and changing the stock and grip to something different if you prefer (I don’t), I’d leave this gun alone.

Overall * * * *
The M4-SML is a back-to-basics gun that runs accurately and reliably, well worth the $1,575 price tag (other guns competing with this quality of a build are often $300-500 more).

comments

  1. avatar Heretical Politik says:

    Does anyone have an accurate count of how many companies build AR-15s? Just curious.

  2. avatar Chad A says:

    I built my first AR a year ago and all said and done the price did creep up higher than I’d originally anticipated and that’s when I started to understand why folks spent $1k+ on an ARs when the gun shops were full of $600 models. That said I was able to match the accuracy of this one for a bit less…

  3. avatar Jon in CO says:

    I don’t understand buying a parts gun when you can do it yourself and save money. I have damn near the exact stuff (sights, furniture, and rail are different, but rail is same manufacturer, SLR rifleworks). If you buy the right stuff at the right sale price, you can do this exact build around 1200.

    1. avatar ActionPhysicalMan says:

      A lot of people would be confused and frustrated trying to buy and mate even a complete upper and a complete lower. Adding an optic would increase the complexity of the task exponentially:-)

    2. avatar ActionPhysicalMan says:

      To be fair, if one does not enjoy buying parts and assembling a rifle and or can make more money in the time it would take to do so, buying a completed one is rational.

      1. avatar Tex300BLK says:

        If you start with a box of completely unassembled parts it literally takes 30mins to 1 hour from when you drive the first roll pin to when you are racking the charging handle on the finished gun. You’d have to be the CEO of a major corporation or one of Bloomberg’s lawyers for the time spent to come into consideration. Most professional gunsmiths only charge between 50-60 to assemble an AR.

        1. avatar AdamTA1 says:

          IF you’re mechanically inclined. You’ve got to remember there are people in this country that don’t know how to change the oil in their car or even a tire. Something that would take you 30 min or an hour to do could be completely impossible for another person.

          I’m not ashamed to admit assembling my first lower which I did recently took me more than a half hour but I also took my time to make sure it was right as I’d never done it before.

  4. avatar Bob says:

    I’d like to see an article with an AR shootout across the price ranges. Not the easiest thing to put together, and not necessarily a cheap endeavor, but I bet it would get referenced a lot.
    A couple in the 400-800, a couple in the 800-1200, a couple in the 1200-1700, and then a couple in the 2k+, or something like that. Comparing: Accuracy/reliability/features and what those features are worth for a intended task (competition vs home defense vs plinking)

    Myself I tend towards spendier ARs (JP enterprises), but that doesn’t resonate well as a recommendation with new shooters. Lately I’ve been working on builds (still with good parts) because I can’t justify the upfront one time expense for 3 or 4 more AR’s with JP, especially when I have a hard time justifying my intended use/need case to the boss.

    I look at building as a way to get exactly what you want part wise or if you just want to spread the cost over time, but still have something in hand vs just saving for a complete rifle. I don’t know that you save any money.

    1. avatar Ing says:

      Yeah, from what I’ve seen as I’ve been planning to build my own (very first) AR, unless you’re incredibly patient and methodical, you’re not going to save money doing it yourself, especially at the low-budget end of things.

      A local FFL offers complete Anderson parts kits (minus sights/optic/magazines) for $425, which is the cheapest I’ve ever seen for a solid low-budget AR build. Sourcing the cheapest individual parts for a similar build over Christmas vacation, the lowest price I could come up with was about $560.

      If I find enough parts on sale, I might get close to the full-kit cost…but it’s just as likely that some crazy thing will start a panic and everything AR-related will actually go up in price. (Then there’s the election, which has its own predictable effect.)

      For me, being on a very tight budget, buying parts over time is the only way I can possibly afford even a very low-budget AR-15. And by spreading the cost over time, I might be able to afford a reasonably nice rifle. Plus which, I’m looking forward to the experience of building it myself. The more I know about my own gun, the better.

      But man, I do wish I had the $$ to buy one of these Sons of Liberty kits. This is pretty much the exact thing I want: the basics, done right.

      1. avatar Partigiano says:

        I built an AR with a side-charging upper from X-Products for ~950 American including MBUIS (no optic yet). It was my first build ever, and yes I scratched the lower a little by misusing a punch, but other than that it went perfectly. Granted I bought the upper on Black Friday and got an insane deal, but regardless I was using mid to high-end parts for everything and still kept it under 1000.

      2. avatar Gruney says:

        The first AR I ever shot is one I built from parts. It got pretty expensive but I used quality parts. I only have fixed iron sights, but I can add an optic and co-witness if I feel like it. Seems to shoot fine given my old eyes and no scope.

        I did lots of research and had no real problems. Should have had a roll pin punch for the trigger guard pin to avoid some minor scratches. Bought the upper assembled on the theory that the part that holds in umpteen PSI of pressure is best assembled by somebody that knows what they are doing.

        I didn’t save money, but I learned a lot about ARs. Some of the design choices are brilliant and some make you scratch your head. I don’t think building it gave me the AR bug. I would really like an M14 or something else more old school, even though I don’t need one.

    2. avatar jwtaylor says:

      Bob, the problem with such a comparison is time, and to some extent money, at least if required for a quality review. I would consider anything less than 500 rounds of multiple types of ammunition through an AR to be less than adequate to determine reliability. And really, on even the mid level ARs, that 500 rounds isn’t going to show you anything. By that I mean, if you have to shoot more than 2,000 rounds straight to get a single malfunction, it is unlikely we will know which AR is more reliable. Because nobody is going to shoot the 20,000 rounds required to prove which AR is more reliable.
      A big separator in quality is accuracy, but even then, so many ARs are MOA guns now that I would consider that the standard. I’ve seen ARs shoot thousands of rounds through them, and still shoot 3/4 MOA, and even 1/2MOA after 500 rounds. But most of the people shooting the guns will never get that level of accuracy, because they can’t shoot well enough for it to matter, or they are shooting poor quality ammunition.
      And then it comes down to look and feel, which is completely subjective. Maybe weight, but not too many people can even tell the difference between a 6lb gun and an 8lb gun, not until you fire it anyway.
      If I only reviewed 6 guns, 2 low, 2 mid, and 2 high end, it would still probably take me a full week of doing nothing but that review, and cost a least a grand in ammo to shoot that many rounds of multiple types. But that’s what it would take to adequately do that comparison.

  5. avatar tsbhoA.P.jr says:

    so put it all together and sell it with an 80% lower without the warranty.
    i equate this gun to the armalite 3gun which demonstrated similar proficiency and cost.
    an ar will never be my go to. honestly i just threw a skinner peep on a 16″ .44 mag and as someone once said, “dat dat.”
    but the lowers and a jig are on their way because i can. maybe not as simple a build as a falling block would be, as dg previously mentioned (like four years ago), but where’s the kit for that?
    if my builds infect me, then this gun is certainly something i see as near ideal- ar wise.
    i’m anxious to get started because project. and freedom.
    get ’em while you can before you can’t.
    because you may soon have a direct infringement on your direct impingement.

  6. avatar Sixpack70 says:

    I’ve built three ARs the past two years. The first DPMS 16″ barrel 5.56 rifle shoots under an inch and with a Nikon P223 3-9x was around $750. The second 20″ LaRue barreled rifle I’m still working on due to a cycling issue, but at 25 yards it shoots into one hole for a cost of about $900. The 16″ 300blk is barely over an inch (it will probably shoot tighter) at 100 yards and was around $850 using a KAK industries pistol gas barrel and Nikon P300 2-7x scope. With what I have built in my garage, and the performance per dollar, I can’t see spending $1500 for something i can make in about 2 hours that performs in a similar manner.

    1. avatar BillC says:

      I’ve built 4 uppers and 2 lowers in the past 10 months. Fvck, it’s addictive. All with decent to bullet-proof parts, but vastly different barrel lengths and barrel materials. I haven’t done any formal accuracy testing, as I mostly just plink steel or practice shooting dynamically (best way to put it) I know a couple of those uppers can well outshoot my crappy vision and normal setup of a red dot. My problem is that home assembly always starts out a cost saving measure, then immediately starts going north of $1k, but that is generally including an Aimpoint Pro or Vortex Viper PST 1-4x w/ ADM mount.

      1. avatar OODAloop says:

        It is addictive. An added bonus is if you reload, so you can roll them in almost any caliber. I’ve built in .22lr, 5.56, 6mm-223, 6.5 Grendel and .300 BLK. The 6mm-223 & 6.5 will do under .5″ @ 100yds, both with Black Hole Weaponry polygonal barrels.

      2. avatar Tex300BLK says:

        “My problem is that home assembly always starts out a cost saving measure, then immediately starts going north of $1k”

        So true, I started out on my first build trying to stick right at or just below 1k and very quickly fell victim to the “hey this fluted stainless steel barrel is only $50 more” and other “ooh something shiny!” moments, ended up closer to $1500 when the dust settled.

        I have a stripped lower sitting around and a box that is slowly accumulating parts for a 6.8spc, going to try and keep it reasonable, however well that is going to work.

  7. avatar Tile floor says:

    I’m with you on the piston. I shot 400 rounds of nasty Tulammo through mine the other day. Zero malfunctions and took maybe 5 minutes to get it immaculately clean.

    That AR looks pretty sweet, but with a couple manufacturers making inexpensive ARs that are of a decent quality, I personally would rather get one of those and gradually upgrade it.

    1. avatar jwtaylor says:

      I shoot just about every AR suppressed now. After spending forever cleaning a DI gun that was suppressed, I shot 200 rounds through an Underground Tactical piston gun that was suppressed. What a difference. The bore took just as long, but the rest of the gun was just a wipe down. Literally 3 cleaning patches was all it took to clean the entire gun and make it shine, other than the bore. After that, I never went back.

  8. avatar jwtaylor says:

    It seems like a lot of you are building ARs with quality parts, but it also seems like many of you aren’t really testing them. How do you know if they are really any good? The parts are not the whole.
    How many of you have more than 5k rounds through your home built AR, without replacing any of the functional parts? How accurate is it at 100 yards now, in inches?

  9. avatar Serafin says:

    SOLGW is a great group! You barely scratched the surface of what they build. Very few people know how much they help and contribute to organizations and regular hard working people. To be honest they go way out of their way to help a lot of folks. I’d recommend them to anyone. My first rifle was an impulse buy wanting to build one for the first time. After the abuse I kept going going back they stand behind a great product! The people that I have suggested go that direction have not taken up my offer yet! ” if you don’t like it I’ll buy it from you full price!”.

  10. avatar 4Adam12 says:

    That’s not a Magpul MOE grip. It’s an Ergo grip. Any other parts tested that are not as listed in the description?

  11. avatar Vernon says:

    I would get this gun just so I can say that Fortune personally oversaw it’s construction.

    1. avatar Robert Farago says:

      Is that yours? Write for us boyo. thetruthaboutguns@gmail.com

      1. That P&S article was written by Matt Shockey.

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