Kythera V2 HPA Conversion Kit, M4/M16

Kythera has been PolarStar’s most anticipated product of the past decade. This HPA system is a radical departure from all previous systems produced by PolarStar, as the Kythera does not use a battery, FCU, or any type of electronics. The Kythera is completely mechanical. This means you will never have to worry about charging batteries or working with delicate electronic devices. It also means the system is fully waterproof.

The name "Kythera" (ky-the-ra) is derived from the Antikythera Mechanism, a mysterious device discovered by sponge divers off the coast of the Greek island of Antikythera. The mechanism had such an advanced design that scientists have been studying it for decades to uncover its purpose. The machine dates back to the late 2nd century BC and is the most sophisticated mechanism known from the ancient world. Nothing as complex is known for the next thousand years. It is now understood that the Antikythera Mechanism was dedicated to astronomical phenomena and functioned as a complex mechanical "computer" that tracked the cycles of the Solar System.

For this reason, we use the name Kythera for the valve mechanism at the core of a new line of PolarStar mechanical HPA systems. Although it contains very few parts and is easy to install and maintain, the system incorporates a highly intelligent design and is unique on the market. The system was designed from the ground up as a mechanical system and uses a realistic trigger mechanism that can be applied to single-shot, semi-automatic, and fully automatic firing systems.

The first of these systems is the Kythera SA (semi-automatic), the semi-only variant for use in AEG gearboxes.

So, what makes the Kythera so unique?

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Realistic Trigger

What sets this system apart from other mechanical systems is its trigger design. The trigger mechanism is engineered to replicate the function, weight, and feel of a real single-action firearm trigger. It feels real because it is real. The hardened steel alloy sears catch and release the stainless steel spool valve in the same way that real firearm sears catch and release the hammer or striker. This gives the Kythera trigger the distinct break and reset you would expect when firing a real single-action firearm. The Kythera SA trigger mechanism is also adjustable, allowing the user to precisely fine-tune the pull weight and overtravel. Additionally, the internal firing valve is balanced, and the only force applied during firing is the main spring. This means the trigger function and feel are independent of input pressure and velocity.

Full Firing Cycle

The Kythera SA design completes a full firing cycle with a single pull of the trigger. This provides the proven closed-bolt performance of the Fusion Engine and F2 in a fully mechanical and waterproof system with a realistic trigger. It does not require the trigger to be released before the nozzle chambers the next round and refills the firing volume. This occurs automatically and consistently with every shot, with adjustable nozzle dwell time and return speed.

Because the system resets and recharges immediately after firing, it is ready to fire again before the trigger is released. This means the system can cycle very quickly for faster follow-up shots and reduced potential for double feeding.

Extremely Efficient and Consistent

The Kythera valve design operates without requiring air to control the opening or closing of the valve. Without a pilot valve, 100% of the air entering the system is fired through the nozzle, allowing it to operate with exceptional efficiency. In addition to being extremely efficient, the system is also extremely consistent. The valve releases at the same point every shot with the same force applied, regardless of trigger input.

Universal Charging Cable

The visible steel cable at the rear of the system is connected to a cocking mechanism for the internal spool valve. Although the system automatically cocks the spool valve when pressurized, since the Kythera uses a balanced valve, it is possible that in certain situations the valve may lock and need to be manually cocked. Typically, this only occurs if the system is run completely out of air, causing the pressure to drop below the operating range. The cable is designed to be routed through the rifle grip for easy access or possibly even attached in some way to the charging handle.

Easy Installation

The Kythera SA system installs into a standard gearbox as a single assembly and generally does not require any modification to the gearbox. There are no separate components to install, and the only parts that must be retained from the gearbox are the trigger, spring guide, selector plate, and safety components.

Wide Velocity Adjustment Range

The Kythera features a wide operating pressure range of 60 psi to 180 psi, allowing you to adjust the system’s velocity and adapt it to different requirements and applications. Within this pressure range, we observed a muzzle velocity of 270–500 fps with 0.20 g BBs using a 6.05 x 380 mm inner barrel. This allows a single Kythera to be used in any role, from CQB to sniper, primarily by adjusting the input pressure of your air system.

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Designed from the ground up as a high-performance mechanical HPA system, not as a modification of a solenoid-operated design.
Patent-pending valve mechanism provides excellent efficiency and consistent velocity combined with a realistic trigger and reset.
Completes a full firing cycle with a single trigger pull, resulting in consistent nozzle movement and fast follow-up shots.
Adjustable trigger. Adjustments include: Pull weight, trigger pull length, and overtravel.
Adjustable nozzle dwell/return speed.
Wide operating pressure range of 60 to 180 psi.