PolarStar “Kythera” HPA Engine for Airsoft Rifles (Model: SA – Ver2 M4)

Introducing the PolarStar Kythera SA Mechanical HPA Engine — the pinnacle of high-performance engineering for airsoft enthusiasts seeking uncompromising reliability, precision, and realism. Designed specifically for Ver.2 M4 gearboxes, this revolutionary HPA (High-Pressure Air) system breaks away from traditional electro-pneumatic designs and instead delivers a purely mechanical, battery-free solution that combines advanced engineering with intuitive function.

Unlike most HPA systems that rely on solenoids and FCUs (Fire Control Units), the Kythera was engineered from the ground up as a mechanical unit. This means no electronics, no batteries, and full waterproof capability — ideal for players who operate in all conditions and demand absolute dependability. At the heart of the Kythera is a patent-pending, balanced valve mechanism that provides a clean, efficient air cycle with consistent velocity and minimal air waste. Every trigger pull results in a full shot cycle, delivering rapid follow-up shots and superior nozzle reset for closed-bolt-like accuracy.

One of the standout features of the Kythera SA is its incredibly realistic trigger design. Inspired by real firearm mechanics, this trigger uses hardened alloy steel sears to catch and release the internal stainless steel spool valve. The result is a crisp, responsive trigger with an authentic break and reset — a feature rarely found in the airsoft world. The trigger system is also fully adjustable for weight, travel, and over-travel, allowing users to fine-tune their setup for precision shooting or high-speed engagements.

Internally, the Kythera is simple yet sophisticated. It completes a shot cycle entirely upon trigger pull, which means you never have to release the trigger for the system to re-cock or chamber the next round. This also prevents double feeding and ensures a smooth, consistent firing experience every time. Additionally, the nozzle dwell and return speed can be adjusted to suit different build configurations, ammo types, or field roles — whether you’re building a CQB rifle or a long-range sniper platform.

With a wide operating pressure range of 60 to 180 PSI, the Kythera allows users to dial in velocity from approximately 270 to 500 FPS using .20g BBs and a 6.05x380mm barrel. This versatile adjustment range makes the Kythera suitable for nearly any style of play, from indoor close-quarters to long-range outdoor engagements.

Another game-changing feature is the universal charging cord. While the system is designed to auto-cock when pressurized, the steel cable can be routed through the pistol grip or connected to the charging handle for manual cocking if necessary — typically only when the system has been fully depressurized.

Installation is incredibly straightforward. The Kythera is a drop-in system for Version 2 gearboxes and typically requires no gearbox modifications. Just retain your selector, safety components, spring guide, and trigger, and you’re ready to go.

The Kythera SA is not just another HPA system. It represents a shift in the airsoft meta toward rugged simplicity without compromising on performance. Its mechanical nature offers reliability in extreme conditions, while its high-efficiency valve and realistic trigger feel elevate the user experience to a level unmatched by other platforms.

Manufacturer: PolarStar Airsoft
Operating Pressure: 60 – 180 PSI
Velocity Range: 270 – 500 FPS (with .20g BBs and 6.05x380mm barrel)
Fire Mode: Semi-Automatic
Compatibility: Version 2 M4 AEG Gearbox

About PolarStar:
Founded in 2009, PolarStar is a U.S.-based engineering company that redefined airsoft with the launch of its patented Fusion Engine. With roots in the automotive racing industry, PolarStar brings advanced mechanical and manufacturing precision to the airsoft world. The Kythera is the latest evolution in their mission to deliver rugged, high-performance HPA systems engineered for professionals and hardcore players alike.

Whether you’re building a DMR or need a dependable workhorse for MILSIM, the PolarStar Kythera is your answer. Built for realism. Engineered for dominance.