BullCraft Classic Army Stoner 96 HPA Gearbox Shell

A purpose-built HPA gearbox shell for converting the Classic Army/Knight’s Armament Stoner 96 to a PolarStar F2 or JACK.

The shell provides dedicated engine alignment, organized FCU and wire routing, and a secure installation without a separate engine shim kit. Dual nozzle-alignment points help keep the engine positioned correctly inside the receiver.

Choose the Correct Configuration

Your required configuration depends on whether you’re using an M249-specific PolarStar engine or converting a standard F2 or JACK.

Gearbox Shell Only

Choose this option if:

• Your M249-specific engine already includes the required nozzle and electronics.

• You already have the required #3 M249 nozzle and fitment components.

Gearbox Shell + Nozzle

Includes the gearbox shell and the required #3 M249 nozzle.

Choose this option if you already have the correct M249-style electronics but still need the proper nozzle for your F2 or JACK.

Gearbox Shell + Nozzle + M249 Fitment Kit

Choose this configuration when installing a standard, non-M249 PolarStar F2 or JACK.

The M249 Fitment Kit includes:

• PolarStar plug board
  

• Trigger switch with JST wire

The trigger switch is included as a backup for builds that no longer have the original switch.

Important Compatibility Information

Standard F2 and JACK Engines

A standard, non-M249 PolarStar F2 or JACK requires:

• A #3 M249 nozzle

• The M249 Fitment Kit

An M249-specific engine does not require the additional fitment kit because the necessary parts are supplied with the engine.

V2 Trigger Boards

This gearbox is not compatible with the PolarStar V2 trigger board. The Stoner 96 body pin interferes with the board’s mounting position.

Core Features

• Designed for the Classic Army/Knight’s Armament Stoner 96

• Compatible with PolarStar F2 and JACK engines

• Dual nozzle-alignment points

• No separate engine shim kit required

• Front wire and FCU pass-through

• Rear FCU storage cavity

• Precision-aligned front engine pin

• Updated design based on installation testing and customer feedback

Before Ordering

Confirm which engine version you have before selecting a configuration. If you aren’t sure whether your engine is M249-specific or uses the standard F2/JACK configuration, contact us before ordering.