
- description
The bolt is where an HPA engine spends its air, so it is also where the gains hide. The XX-Mold reduces air consumption per shot, which means more shots per tank without changing how the gun performs.
That lower demand pays off twice. Because it needs less volume during rapid fire, it stays stable on lower-flow third-party regulators and tank presets that would otherwise fall behind. If your regulator is not a high-flow unit, this is the part that makes the difference.
The adjustable nozzle is the headline. Rather than living with a fixed length, you set the nozzle to sit precisely in your hop-up chamber — which improves grouping and output stability, and synchronises the internal air-cycle rate to deliver the right air volume for your nozzle length and configuration.
It also minimises the shot-down effect, so the transition from semi into full auto is smoother with less drop across a burst. And although MechLabs engineered it for the XX-Mod, it is fully cross-tech compatible with the NEXXUS and ARC platforms, so owners of those engines get the same air performance.
Specifications
| Specification | Detail |
|---|---|
| Type | HPA engine bolt with adjustable nozzle |
| Engineered for | MechLabs XX-Mod |
| Cross-compatible | NEXXUS and ARC platforms |
| Nozzle | Adjustable to fit the hop-up chamber |
| Air consumption | Reduced — more shots per tank |
| Burst management | Lower air-volume demand during rapid fire |
| Regulators | Stable on lower-flow third-party regulators and tank presets |
| Shot-down effect | Minimised for smoother semi to auto transition |
| Brand | MechLabs |
Good to know before you buy
A component rather than a complete engine, and it is already fitted to a new XX-Mod — so this listing is for upgrading a NEXXUS or ARC, or replacing a worn bolt.
Set the nozzle to your chamber rather than leaving it at default. That adjustment is where the grouping and stability gains come from.
Frequently asked questions
Will it fit my NEXXUS or ARC?
Yes. MechLabs engineered it for the XX-Mod but built it cross-tech compatible with both NEXXUS and ARC.
Do I need it if I have just bought an XX-Mod?
No, the engine ships with it. This is for NEXXUS and ARC owners wanting the same air performance, or to replace a worn one.
How much air will it actually save?
MechLabs do not publish a percentage. What they do state is that lower volume demand keeps it stable on lower-flow regulators, which is the benefit most people notice in practice.
What does adjusting the nozzle achieve?
It sets the fit into your hop-up chamber precisely, improving grouping and output stability, and syncs the air-cycle rate to your nozzle length.
Can you fit it?
Yes — we are an authorised MechLabs tech centre and handle this kind of work in the workshop.