Sons of Liberty Gun Works M4 L89 [Review]: Best Duty AR?

Sons of Liberty Gun Works currently has a lot of buzz about their Mk.1 rifle, but the M4 L89 was their finest offering before that noteworthy release.

It’s touted for being rugged, accurate, and duty-rated — used by many law enforcement agencies.

But does the L89 actually rise to that lofty standard?

My experience with the L89 was a little different than most of the firearms I review, but we tested it to our standards all the same.

Keep reading as we run through specs, features, and shooting performance at the range!

Sons of Liberty Gun Works M4-L89

$1999

at Sons of Liberty Gunworks

Prices accurate at time of writing

$1999 at Sons of Liberty Gunworks

Primary Arms (see price)

Sons of Liberty Gun Works L89 Specs & Features

Specs

• Caliber: .223 Wylde
• Capacity: 30+1 (or by magazine)
• Overall Length: 32”
• Barrel Length: 16”
• Height: 7.5”
• Width: 2.5”
• Weight: 6.85 lbs. (8.4 lbs. as tested)
• Comes with: Box, Gen 3 Pmag 30-round, gun lock, owner’s manual.

Features

• Drivelock Handguard System
• SOLGW Liberty Fighting Barrel
• Liberty 2-Stage Trigger

Sons of Liberty Gun Works L89 Backstory

I was fortunate with the L89 in that I got to build it while being taught by Sons of Liberty Gun Works owner, Mike Mihalski, and Master Armorer, Dillon Hoke. Over the course of the 2-day class, I learned a lot about AR-15s and about the particular approach Sons takes with their rifles.

Mihalski was unwavering when detailing this philosophy and set the tone with the first slide. Everything that followed supported this opening proclamation.

Several statements continued to emphasize his philosophy, like pointing out the armorer’s course was a “fighting gun class”, and that we should understand how the “weapon eats and breathes”.

In short, the L89 is an upper-tier, upgraded option for anyone shopping Sons offerings. The EX03 represents their entry model, while the newer Mk.1 holds the distinction of being their pinnacle.

Mihalski supplies many law enforcement agencies with their duty rifles. Having experience in this area, I can tell you the relationship comes from testing and trust established through performance.

Shooting the Sons of Liberty Gun Works L89: Accuracy & Reliability Analysis

Starting with accuracy, I mounted a Vortex Strike Eagle 5-25x56 to shoot groups at 100 yards. After zeroing, I ran a series of different ammo brands and types through, shooting 5-shot groups.

I began with 77-gr Nosler ASP, a match ammunition. The resulting group was a respectable 1.23 inches in size.

Up next, I fired our 55-gr go to practice ammo from AAC. This FMJ round grouped up nicely, coming in at 1.07 inches total.

Using Remington Premier Match, a 69-gr round, I had three very close together, but a couple got away from me, widening the group to 2.97 inches. The story was similar when I tested with Speer Gold Dot.

This 55-gr defensive ammo started out well, but a couple of dropped shots netted a 3.13-inch group. The best group of the day came from Nosler Varmageddon ammo—the 55-gr ammo pulled an impressively tight group of 0.66 inches!

There are a couple of contributors to this accuracy. First, the 16-inch barrel is 41v50 Chromoly with a 1:7 twist, and second, the Liberty two-stage trigger. But more on that later.

For reliability, I fired a variety of ammunition (as above) through several types of magazines. During this test, I loaded up and fired from a number of commercially available magazines.

All magazines inserted, locked up, fed, locked the bolt back on the last round, and dropped cleanly when I pressed the magazine release. Between this full test and other outings, the L89 has enjoyed perfect reliability, despite me being the builder.

The last thing I’ll touch on for this test is the recoil impulse. Because Sons uses a mid-length gas system combined with an A5H2 buffer and extended tube, the impulse is pretty soft to begin with.

I was given an A2 birdcage to cap the build, but I knew I wanted to test the Speed K from Banish on this rifle. The pairing resulted in some pretty ridiculous levels of control.

Shooting from the VTAC barricade, I noticed I was able to hit doubles and triples pretty easily from 50 yards. The gas system, buffer, and suppressor make the gun super easy to control. The dot just sits in your sight picture.

I pushed up to the ten yards and decided to shoot for speed and accuracy. Using a Shooter’s Global shot timer, I fired five shots as fast as I could at a torso-sized steel target.

All five were hits, and the total time was .89 seconds. My splits were .12, so the whole thing was a great combination of speed and control.

Ergonomics: Fit & Feel

With the Vortex Sparc AR and other accessories, the L89 runs a little on the heavy side, tipping the scales at 8.4 lbs. However, the weight does contribute to the controllable recoil impulse.

The exterior of the 7075 aluminum forged receivers is nice, but designed for work. It’s a satin finish (type III hard coat anodizing) that should hold up to years of abuse (and my poor gunsmithing).

I chose much of the ergonomics in this build, but they are very similar to the standard loadout you can currently purchase from Sons of Liberty. For the stock, I chose a Magpul DT.

The DT is a great option because it has solid ergonomics and hooks up well to the shoulder, but the real magic is on the inside. Magpul created a system that applies dual tension to each position and locks it into place, eliminating wobble.

For the grip, I chose the Magpul K2, which is what normally comes on the L89. However, I chose the XL version. I dig the grip’s texture, its straighter angle, and storage area too.

I didn’t know what to expect from a stock Sons trigger, but the Freedom 2-stage is really good. The initial stage is maybe 1-2 millimeters of travel before hitting a defined wall.

Break is very crisp, and reset is immediate, tactile, and audible. This one also proved light, measuring only 2 pounds, 1.4 ounces on a Lyman Digital trigger gauge.

The handguard is very utilitarian but of high quality. MLOK is present at seven positions along the rail, and the Picatinny rail is well done. The lockup is extremely rigid because three mechanisms contribute.

First, there’s a large steel barrel nut that is part of the Drive-Lock system Sons uses. Additionally, you can see the anti-rotation tabs on the rail, but you can’t see the stainless-steel pin that slots between the receiver and rail, holding things even more rigid.

Another great touch is the reinforced, staked-in-place QD wells on the rail. Both of these work very well, and they’re located on either side of the rail, 3 inches from the receiver, in the 10 and 12 o’clock positions.

The receiver features an ambidextrous fire control with a larger switch on the left. The magazine release is standard, located on the right side, while the bolt catch/release is only on the left.

Sons prides itself on bolt carrier groups, noting they use 158 Carpenter steel and high-pressure testing as well as magnetic particle inspection. In addition, the carrier is chrome-lined, as is the gas key, which is also staked and utilizes grade 8 hardware.

Mihalski referred to the AR-15 Technical Data Package (TDP) frequently during the armorer’s course, and it’s clear Sons adheres to its tenets. This document is the original AR-15 blueprint created by Colt, later adopted by the U.S. military.

Improvements We’d Like To See

Having built this rifle from a box of loose parts, I know it inside and out. The only drawbacks that come to mind are its weight and cost, but these are acceptable in my mind because this is a duty-rated rifle.

Some people may complain that a rifle at this price point should have a pinned gas block. The TDP called for a pinned gas block, but this was written when the gas block was forward of the hand guard and part of the front sight.

Modern, low-profile gas blocks benefit from protection under the rail. In addition, Sons uses barrel dimpling and Loctite to secure their gas blocks.

Who Is It For?

The L89 is not an entry-level rifle. It has been upgraded to endure rigorous use. Accordingly, this rifle is a great choice for law enforcement agencies seeking a dependable, accurate rifle.

Because that upper-tier qualification is met, anything short of that, like home defense, would be well served by the L89 if someone wanted to spend the money. While I wouldn’t rule out competition use, there are lighter options out there.

By the Numbers

Reliability: 10/10

I fired the L89 over 500 rounds through a variety of magazines, shooting from various positions. All shots were suppressed, which is harder on the rifle than unsuppressed.

Ergonomics: 7/10

 Ergonomics are very good on the L89, heightened by Magpul furniture. The rifle loses some points for weight and for not having fully ambidextrous controls (bolt catch/release).

Accuracy: 7/10

With a military standard of 3.5" at 100 yards as acceptable accuracy, the L89 did much better, averaging 1.81" across five types of ammunition. The best group was .66".

Customization: 10/10

AR-15s are extremely customizable and enjoy an enormous aftermarket. There are tons of

Value: 8/10

Although the L89 is just under $2,000, it is competitive with similarly priced rifles in the category based on features and performance.

Overall: 8/10

Sons of Liberty Gun Works M4-L89

$1999

at Sons of Liberty Gunworks

Prices accurate at time of writing

$1999 at Sons of Liberty Gunworks

Primary Arms (see price)

Upgrades & Accessories for the Sons of Liberty Gun Works L89

A solid red dot for your rifle is a great addition because it makes aiming easy. The Vortex Sparc AR is perfect for this build.

Vortex Sparc AR Red Dot

$200

at Optics Planet

Prices accurate at time of writing

$200 at Optics Planet

Vortex SPARC II Red Dot

$69

at Palmetto State Armory

Prices accurate at time of writing

$69 at Palmetto State Armory

Amazon (see price)

GunMag Warehouse (see price)

Suppressors are outstanding safety equipment because they help reduce the noise penalty of shooting. I really like the Banish Speed K because it knocks down the sound, but also helps mitigate recoil.

Silencer Central Banish Speed K

$999

at Silencer Central

Prices accurate at time of writing

$999 at Silencer Central

In the same theme of safety, you've got to have good ear pro when shooting. I strongly endorse Shell Shock because they protect your hearing and are comfortable to wear.

ShellShock EXO Pro Elite

$119

at ShellShock

Prices accurate at time of writing

$119 at ShellShock

How We Tested the Sons of Liberty Gun Works L89

I tested the L89 for accuracy and reliability using 500 rounds of ammunition. Accuracy was achieved using a Vortex Strike Eagle 5-25x56 scope, shooting groups at 100 yards while using a CTK Precision P3 Ultimate Gun Vise.

Ammunition consisted of 77-gr Nosler ASP, 55-gr AAC FMJ, 69-gr Remington Premier Match, 55-gr Speer Gold Dot, and 55-gr Nosler Varmageddon. Groups were recorded and later measured for the article.

Reliability was tested over the course of the entire 500 rounds, as well as using a variety of currently available magazines. Hexmag, Magpul T-Mags, Colt (USGI), Mission First Tactical, KCI,  and Magpul Gen 3.

Besides MOA testing, multiple drills were used at varying distances, such as shooting from a VTAC barricade at 50 yards, to gather data on performance and ergonomics. For distances inside 100 yards, a Vortex Sparc AR was used.

Meet the Experts

Sean Curtis was a law enforcement officer for 22.5 years, during which time he held various roles, including SWAT Team Commander and firearms instructor. In the course of his career, he completed multiple trainings related to the AR-15--such as 40-hour SWAT, Tactical Rifle, Witness Protection, and High Risk Warrant Service. Additionally, he attended AR-15 armorer courses taught by JDS Tactical and Sons of Liberty Gun Works. Since retiring, Sean has also completed a Carbine Mastery course with Tactical Performance Center and is a certified AR-15 instructor through USCCA.

These courses, combined with his experience as an AR-15 instructor, have given him a unique insight into how AR-15s function and what features are worth splurging on or passing on.

This review was edited by Editor-in-Chief Jacki Billings, who runs Pew Pew Tactical’s experienced team of reviewers. Jacki has worked as a media professional for close to 20 years, specializing in gun media for almost 10 years. She uses her extensive professional journalism and editing experience to set testing protocols and editorial standards. 

Final Verdict on the Sons of Liberty Gun Works L89

I wasn’t sure what to expect from the Sons of Liberty L89. I had heard good things, but still did not know how the rifle would handle our testing.

There was some question in my mind as to whether my building of this rifle might affect its performance, even though the instruction in the armorer’s course was excellent. My doubt was unfounded.

The L89 was 100% reliable, had an extremely manageable recoil impulse, and was highly accurate with some loads. If I were still in law enforcement, I’d be happy to carry one, so I can recommend this rifle without hesitation.

Will you be purchasing a Sons of Liberty Gun Works L89? Let us know in the comments below, and for even more top AR-15 choices, check out Best AR-15 Rifles (2026): Every Use Case Tested.