Primary Weapons Systems MK111, MOD 2-M, 11.85″ Barrel, Black, Radian Raptor Ambidextrous Charging Handle

The PWS MK111 MOD 2-M is a long-stroke piston AR-15 SBR with an 11.85-inch barrel in .223 Wylde. The MK1 designation identifies this as Primary Weapons Systems’ core piston-driven AR-15 platform; the “11” in MK111 refers to the approximately 11-inch barrel class; MOD 2 is the second-generation design iteration; and M indicates the M-LOK handguard configuration. The .223 Wylde chamber is PWS’s answer to the DI-vs-piston debate’s chamber companion — .223 Wylde accepts both .223 Remington and 5.56 NATO ammunition safely, eliminating the need to choose between two otherwise-identical chamberings.

At 11.85 inches, the MK111 sits close to the MK18 10.3″ class but with meaningfully better dwell time — the extra 1.5 inches of barrel allows the long-stroke piston to cycle more consistently across the widest range of ammunition and suppressor conditions. PWS’s piston system particularly shines when running suppressed: where a DI AR-15 becomes significantly over-gassed when suppressed (requiring an adjustable gas block to compensate), the MK111’s long-stroke piston inherently manages backpressure variation more gracefully. The MK111 MOD 2-M is a suppressor-ready SBR out of the box.

PWS MK111 MOD 2-M SBR Specifications

Primary Weapons Systems: Long-Stroke Piston Authority

Primary Weapons Systems (PWS) is an Idaho-based manufacturer that built its reputation on a single engineering conviction: long-stroke piston operation is inherently more reliable than direct impingement for the AR-15 platform. PWS’s long-stroke piston system — derived from the AK-pattern but redesigned for the AR-15 platform — cycles the action with a single, powerful stroke rather than the brief, pressure-dependent pulse of DI. The result is an AR-15 that cycles reliably across a broader range of ammunition, maintenance conditions, and suppressor backpressure states. The MK1 series is the flagship expression of this engineering — a rifle built for people who understand why the details matter.

Why Buy From Western Sport?

Western Sport is a licensed FFL/SOT dealer in Roanoke, Texas, specializing in NFA transfers since 2007. We are an authorized Primary Weapons Systems dealer carrying their full NFA lineup — SBRs and BDE suppressors. Our team knows the PWS platform and can guide you through selecting the right BDE suppressor for your host rifle. Call 817-393-4000.

FAQ — PWS MK111 MOD 2-M SBR

Why choose a long-stroke piston AR-15 over direct impingement?

Long-stroke piston operation keeps combustion gases out of the action entirely — instead of venting gas rearward into the BCG (which deposits carbon throughout the bolt carrier group), the piston converts gas pressure into mechanical force at the gas block and drives the BCG via a piston rod. The action runs cleaner and cooler. When running suppressed — where backpressure is dramatically increased — a long-stroke piston system’s cycling is less affected by the added pressure than DI. The PWS MK111 MOD 2-M was designed for suppressed use as a primary mission.

What does .223 Wylde offer versus 5.56 NATO or .223 Rem?

5.56 NATO chambers are cut to military spec with more headspace, allowing military-spec ammunition to cycle reliably but producing slightly less precision with .223 Rem commercial loads. .223 Rem chambers are tight and accurate with .223 ammo but can be dangerous with higher-pressure 5.56 NATO loads. .223 Wylde is a hybrid: accuracy closer to .223 Rem, but safe and reliable with both .223 and 5.56 NATO ammunition. It is the ideal chamber for a suppressor-ready precision SBR.

Recent eForm 4 approvals have been coming back in about two weeks or less — see our NFA wait times guide for current figures.