Skip to buy
Add to cart €349,90

FEROX

The HPA upper, engineered around the engine.

Scroll — the film takes it apart, screw by screw.

FR 0001 / 1145

The evolution of HPA performance

Designed around the HPA system, not adapted to it.

FEROX is a premium CNC-machined aluminium upper receiver engineered for HPA builds where reliability, consistency and ease of maintenance are essential. Its rigid structure guarantees perfect alignment between the HPA engine, hop-up chamber and inner barrel.

A dedicated mechanical positioning system means every component returns to its exact position after maintenance — consistent feeding and air seal, with no trial-and-error and no constant tuning. Remove the magic pin and three screws and the engine is in your hand; two more free the whole front assembly.

Index

Four reasons it goes back together the same way, every time.

Each entry is a beat in the film above — select one and the film scrolls to it. Every part returns to an indexed position after service: no shimming, no re-zeroing.

Specification

Built like a tool.

±0.01 mm
Bushing tolerance
3
Screws to the engine
6
Anodized finishes
M4
Platform fitment
Material
CNC-machined aluminium
Finish
Anodized — black, blue, red, purple, silver, gold
Weight
About 50 g more than the SKP carbon fibre upper
Hop-up
Quick-release, indexed to your magazines
Underside
M-LOK slots and bottom rail
Sights
Front and rear mounting holes pre-drilled
Engine access
Magic pin, then three screws
Lower
Most M4 platform lowers, with an HPA gearbox lower

Compatibility

What it runs with.

HPA engines

  • PolarStar F2
  • PolarStar JACK
  • Wolverine Inferno

Hop-up chambers

  • Maxx Model recommended
  • Nexx Speed recommended
  • PolarStar · Retro Arms
  • Most M4-compatible units

Lowers

  • Most M4 platform lowers
  • Best with SKP Lower + SKP Gearbox

Before you order: FEROX requires the lower half of an HPA gearbox — such as the SKP Gearbox — to function correctly. Make sure your build includes a compatible lower gearbox shell.

FEROX CNC aluminium upper receiver, assembled, three-quarter view, Black anodized finish

Ferox cnc aluminium upper

Now €349,90

Color — Black

  • Tax included · worldwide shipping, typically 4–5 working days.
  • Returns within 15 days, unused and in original packaging.

All images on this page are renders. The final product may vary in colour.

Package includes

  • FEROX front
  • FEROX back
  • Engine mounting plate
  • Rear endcap bushing
  • Front bushing
  • CNC front sight
  • Aluminium magic pin
  • Quick-release hop-up mounting system
  • Complete mounting screws

Shipping and warranty

Delivery times vary by region and courier, usually 4–5 working days. All products are covered by warranty and customer support. Returns are accepted within 15 days for unused items in original packaging; sale-priced items cannot be refunded and return shipping is at your cost.

Questions

Before you commit.

Does this work with any M4 lower?
It fits most M4 platform lowers, but the upper needs the lower half of an HPA gearbox, such as the SKP Gearbox, to function. If your build does not have one yet, add it before ordering.
Which engines and chambers fit?
PolarStar F2, PolarStar JACK and Wolverine Inferno engines. For chambers, Maxx Model and Nexx Speed are the recommended pairings, with PolarStar, Retro Arms and most other M4-compatible units also supported.
How much of it comes apart for maintenance?
The magic pin and three screws put you at the HPA engine. The same pin and screws take the front assembly off for the barrel or the hop-up bucking, and one twist releases the CNC hop-up. Everything returns to its own indexed position afterwards.
How does it compare to the carbon fibre upper?
The aluminium version weighs about 50 grams more than the SKP carbon fibre upper. You trade that for rigidity and durability, and handling stays close.
Does the finish change anything mechanically?
No. All six finishes are the same machined part, anodized after cutting, and they all sell at the same price.