The discussion opens with an overview of why Primary Weapon Systems chose a long-stroke piston system instead of direct impingement or a short-stroke design. PWS started from experience with AK-pattern rifles and wanted similar reliability and reputation for durability. To address early piston AR issues like carrier tilt, PWS mechanically links the operating rod to the carrier and keeps everything aligned in the piston tube. Their buffer tube has an internal lip so the carrier actually starts inside the tube, further reducing the chance of deflection and malfunctions. The long-stroke system maintains pressure on the piston longer to create a smoother, push-like recoil impulse. The goal was to keep the ergonomics, controllability, and recoil characteristics people like about DI rifles while reducing maintenance and moving combustion and carbon fouling forward, away from the receiver, especially when running suppressors.
The comparison uses three rifles to represent different operating systems. A Geissele Super Duty serves as the direct impingement baseline. A SIG MCX represents a short-stroke piston platform. The long-stroke piston example is the PWS MK116 (referred to as the Mark16). All three are run with the same suppressor, a SureFire SOCOM 556 RC2 full-size can, to keep conditions consistent. Geissele charging handles are installed on the Geissele rifle and the PWS rifle to minimize differences in gas management at the shooter’s face. The SIG MCX retains its factory charging handle. The hosts explain that piston guns are often better suppressor hosts because many include adjustable gas systems, allowing the shooter to tune gas flow and bolt timing for suppressed use, which can reduce gas blowback and improve comfort.
The conversation turns to why adjustable gas systems matter when shooting suppressed. With a suppressor installed, back pressure increases and can cause the bolt to unlock too early if the gas system is not tuned. By turning the gas down, the bolt stays locked longer, giving the bullet time to exit the barrel and suppressor before the action cycles. This pushes more gas and carbon out through the suppressor and down the bore, and less into the upper receiver and shooter’s face. PWS uses a restriction-style gas system rather than venting excess gas at the block. Their system limits how much gas enters the block while keeping it sealed, which they note can result in roughly 2–3 dB less noise compared to vented piston systems and helps avoid piston pop. This design lets the suppressor do more of the actual sound reduction work instead of dumping gas at the gas block.
The hosts begin live-fire testing with the Geissele Super Duty direct impingement rifle and the SureFire SOCOM 556 RC2 suppressor. Clear eye protection is used to better observe any residue or gas blowback. During firing, noticeable gas reaches the shooter’s face, particularly the right eye, causing some tearing. The rifle is brand new and has not been cleaned or lubricated, which makes the carbon buildup on the distinctive green finish more visible. They note that DI rifles like a well-used Mk18 can become extremely dirty in the bolt carrier group yet still run reliably. However, the test reinforces that with DI, the same combustion and gas work that a piston performs up front is happening inside the receiver, naturally putting more carbon and gas into that area and toward the shooter when suppressed, even though recoil impulse and function remain good.
Next, the SIG MCX short-stroke piston rifle is fired with the same SureFire SOCOM 556 RC2 suppressor. The MCX has an adjustable gas system, and the hosts experiment with its positions. Initial shots still feel somewhat gassy at the shooter’s face. After adjusting the gas setting, they fire again and observe that the rifle does not lock the bolt back, indicating the new position is a lower gas setting. Gas to the face is reduced compared to the DI rifle, though some is still felt in the right eye. The experience suggests that even a short-stroke piston system with adjustable gas can improve shooter comfort over DI when suppressed, as more gas vents forward near the gas block area rather than directly into the receiver, but it does not eliminate gas blowback entirely.
The PWS MK116 long-stroke piston rifle is then tested with the SureFire SOCOM 556 RC2. The rifle’s three-position adjustable gas block is used to show how tuning affects recoil and gas behavior. In position one, which allows the most gas into the system, the rifle has a noticeable thump but runs strongly. Switching to position two softens the feel somewhat while maintaining function. Position three, intended specifically for heavy back-pressure conditions like suppressed fire, produces the softest shooting experience and is described as feeling very good. The hosts note that gas at the shooter’s face appears reduced compared to the DI and short-stroke setups. The test visually demonstrates how the PWS restricted, sealed gas system and multiple settings can tailor the rifle’s behavior with a suppressor, emphasizing smoother recoil and less perceived gas blowback.
The segment closes with an explanation of why PWS chose three gas settings instead of a simple suppressed and unsuppressed configuration. Modern suppressors vary widely in diameter and back pressure. Larger-diameter .30 caliber cans and designs with lower back pressure, such as some HuxWrx (formerly OSS) flow-through models or larger SIG and similar suppressors, often need a mid-level gas setting to maintain reliability without overgassing. On the PWS system, setting two is intended for those lower back-pressure cans, providing enough gas to cycle under normal conditions. Setting three is aimed at higher back-pressure 5.56 cans, especially common 1.5-inch diameter models like the SureFire SOCOM 556 RC2, which tend to create the most back pressure. This three-position approach lets shooters match the gas setting to the suppressor type so the rifle runs reliably while minimizing excess gas and maintaining a comfortable recoil impulse.
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