Fully Built Stubby Polarstar Jack HPA M4

This rifle is part of the KA Tech Refurbished Program, where pre-owned parts are rebuilt, inspected, and tuned into a fully optimized PolarStar HPA platform. While the components may be used, the performance is absolutely unmatched—consistent, responsive, and dialed-in the same way as our premium custom builds.

Every rifle goes through the same performance process:
✔ full teardown & inspection
✔ air-seal optimization
✔ nozzle alignment
✔ chrono logging & deviation testing
✔ speed trigger tuning
✔ feeding & cycling verification

If you want elite shot quality at the best possible value, this is it.

⚙️ Performance Overview

• Engine: PolarStar Jack, cleaned, inspected, and tested

• Consistency: Low FPS deviation through KA Tech air-seal tuning

• Trigger: Precision-tuned for crisp semi-auto response

• Power: PSI-adjustable for indoor/outdoor fields 300-450fps

Even with pre-owned components, these rifles shoot better than most brand-new builds thanks to KA Tech tuning.

🧩 Parts List

• Engine: Polarstar Jack

• Hopup Chamber: MAXX Hopup unit w/flat hop

• Bucking: maple leaf pink 

• Inner Barrel: 6.02

• Trigger: retro arms 

• Additional Upgrades: Stuby Stock, amped black IGL, maxx black magazine release

Parts may show cosmetic wear but have been tested and confirmed 100% functional.

This rifle comes as shown in pictures but without magazine. Extras like fcu, battery, battery charger, magazines, airtank, regulator, and line can be added for extra

♠️ KA Tech Refurbished Guarantee

Refurbished build, premium performance.
Every rifle—new or used—is tuned with the same KA Tech standard:
zero compromises, no shortcuts, and performance you can feel.