Cnc piston for short stroke retroarms 13t (ra-9423)

BRAND RETRO ARMS

CNC-Machined Piston
Material: Nylon GF30%
For Short Stroke 13T Configurations
Weight: 12g

This is a specially extended, reinforced, and significantly lightened piston designed for short-stroke setups with up to 13 teeth.
The piston is optimized for Retro Arms gearboxes but can also be used in standard gearboxes.
Before final installation, it is necessary to check whether the piston can be fully cocked by the 13-tooth sector gear.

This piston differs from standard pistons because it has a longer body while maintaining regular guide dimensions, ensuring less leverage during the piston's short stroke.

The rear section is significantly reinforced to withstand the forces generated by strong springs in TSG, DSG, and SSG setups (often reaching forces of around 19 kg) in combination with rapid load changes due to high fire rates, often up to 60 RPS.
This combination of cadence and forces, along with the usual stresses on standard pistons, is what causes the rear part of the piston to break, ejecting the piston rack into the back of the gearbox.

The piston's body is CNC-milled from nylon with 30% glass fiber reinforcement.
This material has excellent properties, including high wear resistance, tolerance to high temperatures and pressures, and excellent resistance to aggressive oils. It is also highly impact-resistant and lightweight.
The nylon material used is oil-resistant, and while it is not strictly necessary to lubricate the piston body's guide grooves, we have integrated lubrication pockets at the contact points between the piston and the gearbox.

Despite its robust and extended body, we managed to keep the weight relatively low, which is crucial for high-speed builds—only 16.0 g.
We do not recommend enlarging the vent holes, as this could potentially damage the structure.
The piston's weight may vary due to moisture absorption of the material. However, we strongly advise against drying the piston, as moisture absorption significantly enhances the material's strength.

The piston rack is made from high-quality spring steel through CNC machining.
The material used is flexible yet, thanks to heat treatment, also hard and wear-resistant.
Although gluing the piston rack is unnecessary, some customers choose to do so (in that case, we recommend a two-component epoxy adhesive).
For this reason, we leave the racks untreated (without an oil-based surface treatment) after heat treatment, so they are no longer black but dark gray and may have various colored stains.
Before installation, it is advisable to lubricate the piston rack, ideally with silicone grease.

This piston has 13 teeth and is therefore suitable for use with Pandora SS13T gears (8055 or 8059).