Description
Polarstar "Hop Up Thing" Chamber for AEG/HPA M4 V2
The Polarstar "Hop Up Thing" Chamber for AEG/HPA M4 V2 is a precision-machined hop-up chamber designed for standard V2 M4 and M16 airsoft replicas. It is suitable for both conventional AEG builds and HPA conversions, with a focus on consistent adjustment, accurate component fitment and reliable air seal.
The chamber is machined in-house by PolarStar from 6061-T6 aluminium. Unlike cast hop-up chambers, the Hop Up Thing is manufactured to tolerances of approximately ±0.002 inches, or ±0.051 mm. The precise construction helps reduce dimensional variation that could otherwise affect nozzle alignment, inner-barrel fit and hop-up performance.
TDC adjustment for consistent hop
The chamber uses PolarStar’s TDC, or Top Dead Center, slider system. The adjustment mechanism applies pressure vertically through the nub onto the hop-up bucking, helping keep the pressure centred over the inner barrel.
A correctly centred and repeatable adjustment supports consistent backspin and a predictable BB flight path. The system is compatible with 3 × 4 mm hop-up nubs, and a matching round nub is included with the chamber.
Designed for AEG and HPA builds
The Hop Up Thing is designed for standard V2 M4 and M16 replicas with either an AEG gearbox or an HPA conversion. The included 0.305-inch gearbox lip is the standard size used in many V2 AEG installations.
The modular gearbox interface allows the fitment of the chamber to be adapted for different builds. The included barrel-shimming O-rings can be used during installation to adjust the position and reduce unwanted movement between the chamber, inner barrel and surrounding components.
Compatibility and final fitment still depend on the dimensions of the replica, gearbox shell, nozzle, inner barrel and hop-up bucking. The feeding, air seal and BB drop test should always be checked after installation.
Compatible with PolarStar Direct Attachment
The Hop Up Thing is also the required hop-up chamber for the PolarStar Direct Attachment system. Direct Attachment allows a compatible PolarStar F2 or JACK HPA engine to connect mechanically to the chamber, creating a rigid assembly consisting of the HPA engine, hop-up chamber and inner barrel.
The included standard gearbox lip is removed for a Direct Attachment installation. The hop-up chamber is then connected using an engine-specific conversion set:
- PolarStar F2 Direct Attachment Conversion Set for the PolarStar F2
- PolarStar JACK Direct Attachment Conversion Set for the PolarStar JACK
The Direct Attachment conversion sets are sold separately. The Hop Up Thing cannot be connected directly to an F2 or JACK engine without the correct conversion set.
Secure inner-barrel installation
A moulded barrel clip is included to secure the inner barrel to the chamber. Five shimming O-rings are also supplied for adjusting fitment and minimising movement in the installed assembly.
PolarStar also includes an ARO tool to assist with the installation of the small retaining O-rings used in the adjustment mechanism.
Compatibility
- Standard V2 M4 and M16 airsoft replicas
- Suitable for AEG and HPA builds
- Includes a 0.305" gearbox lip used in many standard AEG installations
- Compatible with 3 × 4 mm hop-up nubs
- Compatible with PolarStar F2 Direct Attachment when the F2 conversion set is used
- Compatible with PolarStar JACK Direct Attachment when the JACK conversion set is used
- Direct Attachment conversion sets are sold separately
Installation notes
- Check that the hop-up chamber fits correctly in the selected receiver and outer barrel.
- Confirm that the nozzle enters the chamber centrally and to the correct depth.
- Check magazine fitment and BB feeding before using the replica.
- Perform a BB drop test after installing the inner barrel and hop-up bucking.
- Make sure the hop-up bucking lips do not extend too far into the feed path.
- Use the included shimming O-rings as required to minimise unwanted movement.
- Direct Attachment installation requires a separately sold F2 or JACK conversion set.
- Installation and compatibility checks should be performed by a person familiar with airsoft internals.
Features
- Precision-machined hop-up chamber for V2 M4 and M16 replicas
- Suitable for both AEG and HPA builds
- Machined from 6061-T6 aluminium
- Manufacturing tolerances of approximately ±0.002" / ±0.051 mm
- TDC slider adjustment applies pressure vertically onto the hop-up bucking
- Compatible with 3 × 4 mm hop-up nubs
- Modular and removable gearbox interface
- Compatible with PolarStar Direct Attachment conversion sets
- Moulded inner-barrel clip
- Shimming O-rings included for fitment adjustment
- Manufactured in the USA
Package contents
- PolarStar Hop Up Thing chamber
- 0.305" gearbox lip
- 3 × 4 mm round hop-up nub
- ARO retaining O-ring installation tool
- 5 barrel-shimming O-rings
- Moulded inner-barrel clip
- Required adjustment and assembly components
Not included
- Inner barrel
- Hop-up bucking
- AEG gearbox or HPA engine
- PolarStar F2 Direct Attachment Conversion Set
- PolarStar JACK Direct Attachment Conversion Set
- Replica or other components shown in product images
Technical specifications
- Manufacturer: PolarStar
- Product: Hop Up Thing Chamber for AEG/HPA M4 V2
- Product type: adjustable hop-up chamber
- Compatibility: standard V2 M4/M16 AEG and HPA replicas
- Material: machined 6061-T6 aluminium
- Manufacturing tolerance: approximately ±0.002" / ±0.051 mm
- Hop-up adjustment: TDC slider system
- Compatible nub size: 3 × 4 mm
- Included gearbox lip: 0.305"
- Colour: Medical Metal Gray
- Manufactured in: USA
