Sons Of Liberty Gun Works MK1 – new carbine of the one of SOCOM’s unit

The SOCOM competition required meeting the highest standards of firearms, including advanced tests of durability, accuracy, reliability, and resistance to environmental conditions. According to the manufacturer, its product proved itself in extreme environments—heat, cold, dust, mud, and salt water—while maintaining consistent functionality and effectiveness.

The MK1 carbine selected by SOCOM is intended to represent the result of many years of development, based on Sons of Liberty Gun Works’ extensive experience in creating reliable firearms for both civilian and institutional users. Every component of the weapon was subjected to thorough inspection to maximize utility and reliability, ensuring dependable performance under all conditions.

Images: Sons Of Liberty Gun Works

“This is an incredible honor for Sons of Liberty Gun Works and something I dreamed about when I was building my first rifles in my garage,” said Mike Mihalski, Founder of SOLGW. “Our mission has always been to build the world’s finest fighting rifles for those who go into harm’s way. To have SOCOM select our rifle after such demanding trials is the ultimate validation of that mission.”

CEO Nate Horvath added: “I am incredibly proud of our team for their effort on this project, and excited to officially share the news. The MK1 has already seen strong adoption in the commercial and law enforcement markets, where its performance advantages are immediately clear. While this milestone is significant, our team remains focused on delivering reliable, high-quality, performance-driven fighting rifles to all of our customers. The future of the MK1 family is bright, and there is more to come.”

At first glance, the SOLGW MK1 may appear to be just another AR-15. However, this impression is misleading, as the carbine incorporates numerous original solutions designed to adapt it for highly demanding users. The priority in the project is maximum system robustness and adaptation to an incomparably high intensity of use.

The description of the carbine will be divided into two functional assemblies—the upper receiver group and the lower receiver group.

Upper receiver group

The ‘heart’ of the carbine is formed by barrels with the original 5.56 NATO SOLGW V2 profile. According to Mike Mihalski, founder of SOLGW, the barrel profile was selected to deliver optimal performance and longevity without excessive weight. Importantly, the barrel features additional material around the chamber area, which is intended to provide better balance and minimize point-of-impact shift when heavier muzzle devices are attached.

The barrels employ P3 polygonal rifling, which compared to traditional rifling is said to offer superior performance and significantly extended service life. The gas port in the barrel is designed with a ‘conservative’ diameter, avoiding the over-gassing typical of the AR-15’s direct impingement system (more accurately referred to as internal piston). It is common practice to deliberately over-gas a system to increase reliability, but this simultaneously accelerates component wear. SOLGW chose a different path, using a more restrained gas port, a specially engineered geometry inside the upper receiver (including surfaces guiding the moving group), and carefully selected coatings for both the chamber interior and the moving group (the latter coated with NP3).

According to Mihalski, despite the moderate size of the barrel’s gas port, the carbine maintained reliability in SOCOM testing, proving itself under fouling, in extreme firing positions (straight up, straight down, etc.), and in extreme temperatures.

Images: Strefa Celu (Spółka Jammas)

The MK1 can be equipped with barrels made from three different materials. The first is the commonly used 4150 chrome-molybdenum steel with a chrome-lined bore, finished through a phosphating process. The second option is 416R stainless steel, often employed in precision firearms (the MK1 is also available in longer variants). The third—and most intriguing—option is ARMAD steel, produced by Aubert et Duval. According to Mihalski, this is a ‘new generation steel,’ difficult to obtain and machine, but significantly enhancing firearm capabilities—ARMAD barrels are said to have a service life of over 70,000 rounds. ARMAD barrels in the MK1 are chrome-lined and finished using the QPQ (Quench-Polish-Quench) method.

Equally important are the changes introduced in the handguard and upper receiver, which are original SOLGW designs. The handguard, mounted in a way that makes the barrel free-floating, features an M-LOK mounting system across nearly its entire surface, except for the top, reserved for a continuous Picatinny rail. In the middle of the rail—both on the handguard and the receiver—a channel has been created to facilitate cable management for accessories (such as those from flashlights, lasers, and other devices connected to multifunctional switches). Another distinctive feature of the handguard is a laser-textured gripping surface, improving handling security.

Most importantly, innovations were applied in the area where the handguard connects to the upper receiver. The handguard is mounted on a titanium barrel nut with a special coating that enhances heat dissipation from the heated barrel. Cooling is further aided by vent holes on the sides and top of the handguard. The mounting is secured with screws and special nuts at the bottom of the handguard, ensuring precise clamping to the receiver. Rigidity of the connection is further reinforced by two additional solutions:

• Steel pins extending from the upper part of the handguard, fitting into cuts in the receiver.
• Special lugs on the handguard that engage with the reinforced portion of the receiver around the chamber area.

All these solutions are intended to provide the strongest possible connection between the handguard and the receiver, which is crucial when using numerous accessories that add weight to the handguard.

Further changes in the upper receiver include a different method of mounting the ejection port cover. In the MK1, its pin is installed from the opposite side, which allows for easy removal without the need to disassemble the handguard.

Lower receiver group

Fewer changes were introduced in the lower receiver compared to the upper receiver. The trigger guard is an integral part, and the magazine well features a flared opening to make magazine insertion easier. A significant modification in the controls is the enlarged bolt catch lever. According to Mihalski, a stronger spring was also used with it due to the greater mass of the lever itself—this is one example of details that can have a meaningful impact on the reliable operation of the weapon.

The only ambidextrous controls on the MK1 are the safety selector and the charging handle. In many modern carbines, fully duplicated controls are found on both sides—so why is the MK1 different? Their absence is justified by a focus on structural simplicity and reliability. Each duplicated control means additional components, springs, screws, and cuts in the receiver. This increases mechanical complexity and potential susceptibility to malfunctions caused by contamination or damage to extra parts.

Observing photos of soldiers from various armed forces equipped with carbines featuring additional controls, one can sometimes notice them being blocked with plastic ties. An example is left-side magazine releases, which—even when surrounded by protective fences—were still prone to accidental activation by a soldier’s gear.

A fairly significant change compared to the standard M4 is the use of the A5 buffer system. The A5 system features a much longer buffer tube, accommodating a heavier buffer and a stronger, longer spring. This solution is intended to optimize weapon performance under different conditions, with varied ammunition and muzzle devices. The A5 system is sometimes cited as one of the best upgrades that can be introduced to a standard AR-15.

At first glance, the MK1 may appear to be just another AR-15, but in reality it is a highly specialized tool designed for a narrow group of users. Derived from the proven and globally recognized Stoner standard, the MK1 represents a significant enhancement of that platform. It is not a design that immediately stands out with additional controls or radically different geometry. Instead, attention has been devoted to the most critical details, which together create a simple yet robust and reliable construction. Compared to other carbines on the market aimed at similar users, the MK1 distinguishes itself with a certain restraint and modesty, behind which lie numerous refinements to an already well-proven platform. While civilian shooters, sportsmen, or standard infantry soldiers may not notice a dramatic leap in quality, users who subject their weapons to intensive use in extreme conditions should recognize the many benefits. The customer speaks for itself—units subordinate to the U.S. Special Operations Command are equipped with the best firearms, which must withstand incomparably more intensive use and, consequently, greater risk of accelerated wear and damage.

While domestic special units employ H&K HK416/HK416A5 carbines, which structurally differ significantly from the AR-15, the Americans remain largely ‘faithful’ to Stoner’s original principles. The U.S. has also used (and in some places continues to use) the German carbine distinguished by its short-stroke piston gas system, but subsequent procurements have primarily favored designs with the DI gas system (sometimes slightly modified). The gas system commonly known as direct impingement (DI), more accurately referred to as the internal piston, is often criticized for increased fouling of the bolt carrier group and upper receiver, frequently exacerbated by suppressor use.

Standard suppressors cause backpressure, which in turn leads to gas blowback. This results in more gases being directed into the receiver, meaning not only greater component wear and fouling, but also increased exposure of the shooter to harmful combustion byproducts. The advantage often advertised for piston systems is the reduction of this phenomenon, though many specialists point out that the primary path of returning gases is not the DI tube but the barrel itself. Today, flow-through suppressors are becoming the standard, significantly reducing the negative effects of backpressure (some manufacturers claim up to 80% reduction). So is the piston system truly superior to DI? Apparently, American commandos do not see this advantage, as evidenced by the contract for the SOLGW MK1 and carbines from other manufacturers in similar programs.

Of course, this does not mean that piston-driven designs are inferior. The debate among industry specialists and enthusiasts remains open and is unlikely to be definitively resolved anytime soon. Depending on the design, both systems are implemented differently, and it is safe to assume that—when properly executed—they are parallel in terms of effectiveness.

The SOLGW MK1 exemplifies the refinement of existing solutions to perfection rather than ‘reinventing the wheel.’ Many new platforms must first pass through the so-called teething problems stage, during which fundamental design and quality issues may be revealed. The MK1 is based on a well-known and proven platform. It introduces new, original solutions but—importantly—retains backward compatibility with key components of the M4/M4A1 standard.

In 2024, Strefa Celu (Jammas Company) became the official distributor of Sons Of Liberty Gun Works (SOLGW) in Poland. The distribution is intended not only to include a wide range of models in the offer, but also to establish comprehensive after-sales support and services related to the American manufacturer’s products. The MK1 carbines are already available in specific configurations alongside other SOLGW models.

Check the Sons Of Liberty Gun Works offer in Strefa Celu

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