{"product_id":"polarstar-kythera-hpa-engine-for-airsoft-rifles-model-sa-a-k-sr-26","title":"PolarStar \"Kythera\" HPA Engine for Airsoft Rifles (Model: SA - A\u0026K SR-25)","description":"\u003cp data-start=\"0\" data-end=\"98\"\u003e\u003cstrong data-start=\"0\" data-end=\"98\"\u003ePolarStar Kythera® SA HPA Engine — Mechanical High-Performance Power for A\u0026amp;K SR-25 (Model: SA)\u003c\/strong\u003e\u003c\/p\u003e\r\n\u003cp data-start=\"100\" data-end=\"597\"\u003eThe \u003cstrong data-start=\"104\" data-end=\"129\"\u003ePolarStar Kythera® SA\u003c\/strong\u003e is a ground-up mechanical HPA engine built for shooters who want uncompromising consistency, a realistic trigger feel, and rock-solid reliability — all without batteries, electronics, or solenoids. The Kythera SA (A\u0026amp;K SR-25 model) brings PolarStar’s precision engineering to a fully mechanical platform, delivering a responsive single-action trigger, wide operating range, and surgical repeatability that make it ideal for DMR, competition, and multi-role AEG builds.\u003c\/p\u003e\r\n\u003cp data-start=\"599\" data-end=\"1092\"\u003e\u003cstrong data-start=\"599\" data-end=\"651\"\u003eReal mechanical design — no electronics required\u003c\/strong\u003e\u003cbr data-start=\"651\" data-end=\"654\"\u003eUnlike solenoid-based or FCU-dependent HPA systems, the Kythera SA is a purely mechanical engine. That means no batteries to charge, no firmware to manage, and virtually no electronics to fail. The system is waterproof by design and uses a \u003cstrong data-start=\"894\" data-end=\"928\"\u003epatent-pending valve mechanism\u003c\/strong\u003e engineered for maximum efficiency: 100% of the air routed into the engine is available for the shot cycle, producing consistent velocity and excellent gas economy.\u003c\/p\u003e\r\n\u003cp data-start=\"1094\" data-end=\"1657\"\u003e\u003cstrong data-start=\"1094\" data-end=\"1129\"\u003eAuthentic, tunable trigger feel\u003c\/strong\u003e\u003cbr data-start=\"1129\" data-end=\"1132\"\u003eA defining strength of the Kythera SA is its \u003cstrong data-start=\"1177\" data-end=\"1212\"\u003erealistic single-action trigger\u003c\/strong\u003e. Hardened alloy sears engage and release a stainless-steel spool valve just like a firearm’s sear and hammer — giving a genuine break and reset. The trigger is fully \u003cstrong data-start=\"1379\" data-end=\"1393\"\u003eadjustable\u003c\/strong\u003e (weight, length of pull, and over-travel), so you can fine-tune the feel to match competitive disciplines or personal preference. The internal firing valve is spring-balanced, so trigger feel remains consistent regardless of input pressure or external conditions.\u003c\/p\u003e\r\n\u003cp data-start=\"1659\" data-end=\"2194\"\u003e\u003cstrong data-start=\"1659\" data-end=\"1727\"\u003eComplete shot cycle on trigger pull — rapid, reliable follow-ups\u003c\/strong\u003e\u003cbr data-start=\"1727\" data-end=\"1730\"\u003eThe Kythera completes a full shot cycle on the trigger pull, providing closed-bolt reliability akin to PolarStar’s Fusion and F2 platforms. Because the system chambers and recharges automatically without requiring trigger release, follow-up shots are rapid and consistent with a reduced risk of double feeds. No pilot valves are used, and the valve releases at the same point and force every shot — a design that yields both efficiency and predictable performance.\u003c\/p\u003e\r\n\u003cp data-start=\"2196\" data-end=\"2727\"\u003e\u003cstrong data-start=\"2196\" data-end=\"2254\"\u003eAdjustable dwell, nozzle speed and wide pressure range\u003c\/strong\u003e\u003cbr data-start=\"2254\" data-end=\"2257\"\u003eTuning is straightforward and flexible. The Kythera allows \u003cstrong data-start=\"2316\" data-end=\"2356\"\u003eadjustable nozzle dwell\/return speed\u003c\/strong\u003e to control timing, and it accepts input pressures from \u003cstrong data-start=\"2412\" data-end=\"2429\"\u003e60 to 180 psi\u003c\/strong\u003e. In testing (with a 6.05×380 mm barrel and 0.20 g BBs), this pressure window produced velocities from \u003cstrong data-start=\"2532\" data-end=\"2559\"\u003e~270 fps up to ~500 fps\u003c\/strong\u003e, making one Kythera capable of roles from CQB to DMR simply by changing regulator pressure — perfect for players who want a single engine to cover multiple playstyles.\u003c\/p\u003e\r\n\u003cp data-start=\"2729\" data-end=\"3334\"\u003e\u003cstrong data-start=\"2729\" data-end=\"2770\"\u003eDurable, serviceable, and field-ready\u003c\/strong\u003e\u003cbr data-start=\"2770\" data-end=\"2773\"\u003eThe Kythera’s balanced spool valve and mechanical cocking mean the system is extremely robust. A \u003cstrong data-start=\"2870\" data-end=\"2897\"\u003euniversal charging cord\u003c\/strong\u003e is provided for manual cocking if the system ever runs fully out of air — a rare situation — and can be routed through the grip or secured near the charging handle for convenient use. Installation is designed to be simple: the Kythera installs into a standard gearbox as a single assembly with minimal retained gearbox parts (trigger, spring guide, selector and safety). No external electronics or complex wiring harnesses are required.\u003c\/p\u003e\r\n\u003cp data-start=\"3336\" data-end=\"3372\"\u003e\u003cstrong data-start=\"3336\" data-end=\"3370\"\u003eWhy builders choose Kythera SA\u003c\/strong\u003e\u003c\/p\u003e\r\n\r\n\u003cul data-start=\"3373\" data-end=\"3902\"\u003e\r\n \t\u003cli data-start=\"3373\" data-end=\"3445\"\u003e\r\n\u003cp data-start=\"3375\" data-end=\"3445\"\u003e\u003cstrong data-start=\"3375\" data-end=\"3400\"\u003eMechanical simplicity\u003c\/strong\u003e — no batteries, FCU, or solenoids to fail.\u003c\/p\u003e\r\n\u003c\/li\u003e\r\n \t\u003cli data-start=\"3446\" data-end=\"3541\"\u003e\r\n\u003cp data-start=\"3448\" data-end=\"3541\"\u003e\u003cstrong data-start=\"3448\" data-end=\"3469\"\u003eRealistic trigger\u003c\/strong\u003e — adjustable weight, travel, and over-travel for a firearm-like pull.\u003c\/p\u003e\r\n\u003c\/li\u003e\r\n \t\u003cli data-start=\"3542\" data-end=\"3647\"\u003e\r\n\u003cp data-start=\"3544\" data-end=\"3647\"\u003e\u003cstrong data-start=\"3544\" data-end=\"3579\"\u003eFull shot cycle on trigger pull\u003c\/strong\u003e — faster, more consistent follow-ups and closed-bolt reliability.\u003c\/p\u003e\r\n\u003c\/li\u003e\r\n \t\u003cli data-start=\"3648\" data-end=\"3747\"\u003e\r\n\u003cp data-start=\"3650\" data-end=\"3747\"\u003e\u003cstrong data-start=\"3650\" data-end=\"3669\"\u003eHigh efficiency\u003c\/strong\u003e — patent-pending valve uses air direct to the nozzle for excellent economy.\u003c\/p\u003e\r\n\u003c\/li\u003e\r\n \t\u003cli data-start=\"3748\" data-end=\"3816\"\u003e\r\n\u003cp data-start=\"3750\" data-end=\"3816\"\u003e\u003cstrong data-start=\"3750\" data-end=\"3771\"\u003eWide tuning range\u003c\/strong\u003e — 60–180 psi supports CQB to sniper roles.\u003c\/p\u003e\r\n\u003c\/li\u003e\r\n \t\u003cli data-start=\"3817\" data-end=\"3902\"\u003e\r\n\u003cp data-start=\"3819\" data-end=\"3902\"\u003e\u003cstrong data-start=\"3819\" data-end=\"3843\"\u003eWaterproof operation\u003c\/strong\u003e and field serviceability with the universal charging cord.\u003c\/p\u003e\r\n\u003c\/li\u003e\r\n\u003c\/ul\u003e\r\n\u003cp data-start=\"3904\" data-end=\"3931\"\u003e\u003cstrong data-start=\"3904\" data-end=\"3929\"\u003eModel \u0026amp; Compatibility\u003c\/strong\u003e\u003c\/p\u003e\r\n\r\n\u003cul data-start=\"3932\" data-end=\"4031\"\u003e\r\n \t\u003cli data-start=\"3932\" data-end=\"3993\"\u003e\r\n\u003cp data-start=\"3934\" data-end=\"3993\"\u003e\u003cstrong data-start=\"3934\" data-end=\"3944\"\u003eModel:\u003c\/strong\u003e Kythera® SA — A\u0026amp;K SR-25 specific configuration\u003c\/p\u003e\r\n\u003c\/li\u003e\r\n \t\u003cli data-start=\"3994\" data-end=\"4031\"\u003e\r\n\u003cp data-start=\"3996\" data-end=\"4031\"\u003e\u003cstrong data-start=\"3996\" data-end=\"4013\"\u003eManufacturer:\u003c\/strong\u003e PolarStar Airsoft\u003c\/p\u003e\r\n\u003c\/li\u003e\r\n\u003c\/ul\u003e\r\n\u003cp data-start=\"4033\" data-end=\"4454\" data-is-last-node=\"\" data-is-only-node=\"\"\u003eFor players and technicians who demand a responsive, dependable HPA solution without the hassle of electronics, the \u003cstrong data-start=\"4149\" data-end=\"4173\"\u003ePolarStar Kythera SA\u003c\/strong\u003e is a revolutionary mechanical engine that blends analog reliability with modern tuning flexibility. Convert your A\u0026amp;K SR-25 into a high-performance, battery-free platform and experience the refined trigger feel and consistent shot-to-shot performance that only Kythera can deliver.\u003c\/p\u003e","brand":"Polarstar","offers":[{"title":"Default Title","offer_id":47468121653478,"sku":null,"price":445.0,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0793\/6393\/2390\/files\/a313b275-pstar-19157-removebg-preview.png?v=1774002161","url":"https:\/\/ngrwzj-i1.myshopify.com\/products\/polarstar-kythera-hpa-engine-for-airsoft-rifles-model-sa-a-k-sr-26","provider":"CQC Airsoft ","version":"1.0","type":"link"}