Developed from the M16 rifle, the M4 carbine was never meant to be a frontline service weapon. Designed for rear echelon troops, special operations forces fielded the M4 for its light weight and compact size. But the strain of high-volume firefights and heavy firing schedules led to barrel bursts and other failures with the carbine. Following improvements like the SOCOM profile barrel and the adoption of the M4A1, the carbine remains in service with American operators.
Related: The War on Terror’s iconic FN SCAR is dead
During the Global War on Terror, the M4 platform continued to evolve, with newer upper receivers such as the Daniel Defense Block II and the Geissele URG-I. Despite the Army’s adoption of the M7 rifle and the 6.8x51mm cartridge to replace the M4 and 5.56x45mm, SOCOM has doubled down on the system with a new 5.56 weapon: the Sons of Liberty Gun Works MK1 Combat Assault Rifle.
On Nov. 20, 2025, Sons of Liberty announced that SOCOM awarded the company a contract under the Combat Assault Rifle program. A specific unit within the command was not specified, nor was a contract value. However, SOLGW did confirm to We Are The Mighty that the program was in the works for nearly two years, from Request for Information (RFI) to award.
Interestingly, the name given to the new rifle by SOCOM is extremely similar to the Special Operations Combat Assault Rifle, better known as the FN SCAR. To be clear, MK1 is SOLGW’s internal name for the rifle. Perhaps the most notable feature of SOCOM’s new rifle is its 11.5-inch barrel. The M4 uses a 14.5-inch barrel with a carbine-length gas system; the shorter Mk18 uses a 10.3-inch barrel with the same gas system. This results in a more violent operation that wears parts down faster. The MK1’s 11.5 inches has become a go-to “sweet spot” barrel length for firearms manufacturers to achieve reliable and smooth operation with a short barrel.
SOLGW also confirmed to We Are The Mighty that the MK1’s barrel is made of AMRAD steel, designed to offer significantly increased barrel life. The titanium vented barrel nut also uses the same coating found on re-entry vehicles to delay heat build-up and allow faster cooling. At the other end of the operating system, the MK1 features an intermediate-length buffer system to provide less felt recoil and increased reliability, even when the weapon is suppressed.
Ergonomically, the MK1’s rail really stands out. It has a laser-engraved texture to maximize grip without the need to add rail covers that increase the rail’s size and restrict cooling. A channel at the top provides integrated cable management for lights, lasers, and other rail-mounted electronics. On that note, three points of lock-up on the rail help to minimize laser movement and barrel deflection. Contract rifles will also feature an anodized gray finish.
“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, who founded SOLGW in 2014, in a press release. “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.”
Overall, the SOLGW MK1 is an evolution of the tried-and-true M4 carbine. With the latest technology, designs, and materials, Eugene Stoner’s original AR-15 design persists as a premier choice for the warfighter. Though SOLGW is a newer company with no prior U.S. military contracts, the MK1’s selection by SOCOM is as much a vote of confidence in the manufacturer as in the weapon system. SOLGW told We Are The Mighty that the contract rifles will be delivered in early 2026.
