PolarStar JACK Nozzle — 21 Numbered Sizes

Nozzle length is the most commonly overlooked detail in an HPA conversion, and the one most likely to produce symptoms that look like an engine fault. Wrong length and you get misfeeds, poor air seal and inconsistent velocity — none of which the engine is actually responsible for.

The reason it matters is that gearbox shells, hop-up positioning and internal tolerances vary between manufacturers, and sometimes between two versions of the same rifle. PolarStar therefore number their nozzles rather than naming them after a rifle model. Once you know your number, it generally carries across every PolarStar engine using the numbered system — with the exception of some model-specific Kythera setups.

The chart below is PolarStar’s own compatibility data, including tip length and overall length for each nozzle. If your rifle is not listed, the dimensions let you measure and match rather than guess.

Specifications

Good to know before you buy

Confirm your number before ordering. The platforms in the chart are the most common applications, but fitment varies between manufacturers — two rifles of the same model from different brands can need different nozzles.

If your rifle is not listed, PolarStar publish a measuring formula for centreline nozzles: TIP = F + B - (A/2) - 0.0875. The measured tip length needs to fall within ±0.010 inch of a production nozzle. Outside that range, no production nozzle currently exists for the platform — send us your measurements and we will check.

Frequently asked questions

How do I find my nozzle number?
Use the chart above to match your rifle. If it is not listed, measure your original gearbox and nozzle and apply the formula in the section above, or send us the rifle details and we will work it out.

Why are they numbered rather than named?
Because gearbox dimensions vary between manufacturers making the same rifle. A number describes the actual length; a rifle name would not.

Will the same number work on my other PolarStar engine?
Generally yes — the numbered system is shared across PolarStar engines that use it. Some model-specific Kythera systems are the exception.

What happens if I use the wrong one?
Misfeeds, poor air seal and inconsistent FPS — all of which look like engine problems but are not. It is worth getting right first time.

Do I need a new nozzle when changing rifles?
If the gearbox dimensions differ, yes. That is exactly what the numbered system exists to handle.