MechLabs XX-Mod HPA Engine

The HR556 is based on the MechLabs XX-Mod engine, a fully mechanical HPA engine for the V2 gearbox. This design makes it the ideal base for this replica.

Why this engine is perfect for the HR556:

Mechanical system: no electronics, no cables, no sensitive components. This ensures maximum reliability, especially under extreme conditions.

Extremely robust construction: The XX-Mod is designed to last. Fewer moving parts, clean power transmission, and a very direct firing behavior.
Consistent performance: Smooth shooting, reproducible behavior and a well-defined trigger feel – exactly what AS Helden wants for the HR556.

Easy maintenance and service: The simple and well-thought-out design makes the engine not only robust but also easy to handle in everyday use.

The MechLabs XX-Mod engine is not a marketing gimmick, but a conscious choice to use a reliable mechanical system that perfectly embodies the HR556 philosophy: functional, durable and absolutely practical.

The MechLabs ROTO hop-up chamber sets new standards in the HPA (High Performance Airgun) category and revolutionizes the traditional hop-up system. Unlike conventional hop-up chambers, the ROTO eliminates the need for a hop-up rubber. Instead, a precision-engineered, integrated contact pad generates exceptionally consistent backspin, resulting in excellent consistency and shooting accuracy. The innovative "Buckingless" technology eliminates typical weak points such as worn or displaced hop-up rubbers, ensuring consistently high performance, especially with powerful HPA configurations and heavy pellets.

The MechLabs ROTO hop-up chamber sets new standards in the HPA category and revolutionizes the classic hop-up system. The Helden HR556 Airsoft combines the MechLabs ROTO hop-up chamber with a precision-machined motor. The 292mm long, precision-machined 6.03mm inner barrel provides an optimal balance of air volume, efficiency, and accuracy, significantly contributing to the HR556's exceptional consistency and range. The combination of MechLabs mechanical technology, the ROTO rubber-less hop-up, and the precision-machined 6.03mm barrel makes the HR556 a no-compromise, high-end HPA system for players who demand maximum performance and reliability.


S-HPA HR556 10" Rifle
T6 aluminum upper receiver
Reinforced polymer lower receiver
M Lok compatible aluminum handguard with 4 side slots and 5 under the barrel
190-round polymer mid-cap magazine
Folding polymer stock with rubberized shoulder pad and QD sling attachments
7075 aluminum inner tube
Dual profile flip-up sights
14mm counterclockwise (ccw) thread
HPA MechLabs XX-Mod Engine
MechLabs ROTO Adjustable Aluminum Hop-Up TDC
Firing modes: safe, single, full auto
Adjustable RPS motor, operating pressure 100-120 psi, minimum 80 psi, maximum 200 psi, TS Regulator ready
Aluminum magnetic trigger
Precision inner barrel length 6.03 x 292mm
Length: 580mm - 785mm
Weight: 2103g
Black color
Carrying bag included