PolarStar Direct Attachment — F2 and JACK Front Cylinder
PolarStar Direct Attachment — F2 and JACK Front Cylinder
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DETAILS
DETAILS
- description
On a conventional build the upper gearbox shell is what holds the engine in line with the hop unit. That is a lot of responsibility for a moulded or cast shell, and it is why people lose evenings to shimming: half a millimetre of nozzle tilt is enough to spoil a grouping, and you cannot see it from the outside.
This removes the shell from that job entirely. It is a two-piece set — a front cylinder that replaces the original on your engine, plus an internal adapter — and the Hop Up Thing screws directly into it. Once it is together the engine, the hop unit and the inner barrel are a single rigid piece of metal. There is nowhere for the nozzle to lean as it loads a round, which means each BB is picked up the same way, which is where consistent hop and tighter groups actually come from.
Alignment stops being something you chase and becomes a property of the parts. PolarStar's own framing is blunt about it: with the thread done up, it is not physically possible for the nozzle to be out of line with the bore.
What you still need is somewhere to put the electronics. Because the upper shell is no longer doing any aligning, you can house the trigger, selector and wiring in a modified shell, a printed lower or a fully custom chassis — PolarStar built this with scratch builds and 3D-printed projects in mind as much as fixing an existing gun. It is a building block, not a drop-in.
Specifications
| Specification | Detail |
|---|---|
| Function | Replaces the front cylinder on an F2 or JACK engine |
| Supplied as | Direct attach front cylinder plus internal adapter |
| Engine fitment | F2 or JACK, matched to the version you choose |
| Hop unit interface | Threads directly to the PolarStar Hop Up Thing |
| Result | Engine, hop unit and inner barrel form one rigid assembly |
| Gearbox shell | No longer required for alignment; still needed to house electronics |
| Not included | Engine, hop unit, gearbox shell or chassis, inner barrel |
| Brand | PolarStar |
Good to know
Which one do I need? Match it to your engine — the F2 version for an F2, the JACK version for a JACK. They are not interchangeable.
Does it come with the hop unit? No, and it does nothing without one. It is designed around the PolarStar Hop Up Thing, which is a separate purchase.
Do I still need a gearbox shell? Not for alignment, but the trigger, selector and electronics have to live somewhere. A modified shell, a printed lower or a custom chassis all work.
Will this work in a normal rifle? Yes. Plenty of people fit it to a standard build simply to cure a shell that will not hold alignment.
Is it a performance part or an engineering part? Both, but the gain is indirect: it does not add power, it removes the movement that was costing you consistency.