[SPARK] Hiei-kai High-Precision Inner Barrel 6.05mm ID [EVOLT Exclusive 229mm] (Restock expected after June 2026 / Pre-order)

The ultimate inner barrel that satisfies SPARK custom engineers with its performance.

It can dramatically improve the accuracy of Tokyo Marui's new EVOLT.

The "Hiei®" is a purely domestic, high-quality, ultra-precision inner barrel developed with the concept of SPARK and the cutting-edge metal processing technology of artisans from "da Vinci," the manufacturer behind the custom barrel "Guren / Raizen" series. Further improvements have been made to various parts, resulting in the birth of the "Hiei® Kai," the ultimate, refined inner barrel.

The base material used is a premium domestic stainless steel produced by cold forging, meticulously crafted by Japanese artisans using high-precision domestic CNC machines.

To ensure stable HOP application, the HOP window shape and polishing are meticulously attended to. The barrel's end features an ultra-long 20mm taper, designed so that a layer of air envelops the BB bullet! The synergy with the tight 6.05mm diameter improves initial velocity, accuracy, and range.

The "Hiei" inner barrel for airsoft guns is a registered trademark of SPARK Co., Ltd.

【Features of Hiei® Kai】

Ultra-polished HOP window

• For a stable trajectory, a stable "hop-up effect" is crucial.
• Artisans meticulously polish the inner wall, including around the HOP window, to eliminate uncertain factors affecting the BB bullet.
• The HOP window undergoes "round cutting," a very difficult machining process, which ensures smooth movement of the HOP packing and maximizes its performance.

20 mm ultra-long taper

• Extremely hard cold-forged stainless steel is very difficult to machine due to its hardness, requiring high-precision CNC machines and skilled artisans to select cutting tools and create precise machining programs. The extraordinary 20mm ultra-long taper suppresses sudden changes in resistance around the barrel exit and an increase in turbulence coefficient, eliminating adverse effects on accuracy.
• This maximizes the inherent accuracy of the gun.

Pride in Japanese manufacturing

• The intricate round cutting of the HOP window, the polishing of the barrel's inner surface, and the long taper processing on the muzzle side are easy to describe in words, but creating an ultra-precision inner barrel from difficult-to-machine cold-forged stainless steel requires high technical skill.
• The "Hiei® Kai" is a MADE IN JAPAN product, a source of pride for Japan worldwide.