G&G M120 Grade Upgrade Airsoft AEG Gearbox Spring - 370 - 400 FPS

Swapping your spring is the most direct way to change what velocity your AEG produces, and the G&G M120-grade spring pushes into the 370–400 FPS range on 0.20g BBs — which is where most outdoor fields enforce their cap. If your stock spring is an M80 or M90, this is a noticeable step up. If you're already running an M115+, the gain is marginal.

AEG springs are standard across gearboxes, so this one will drop into any AEG that takes a conventional spring. Heavier springs put more load on the piston and shafts, so it is worth pairing the swap with a metal spring guide and upgraded bushings. It is common practice rather than a hard requirement.

The trade-offs are mechanical, not cosmetic. A heavier spring means more current draw from the motor, which means a battery that can deliver the discharge, and a MOSFET becomes the thing that saves your trigger contacts from burning out faster than normal. A high-torque motor handles the load better than a speed motor. None of that is a requirement, but it is how the chain works.

One note on V2 gearboxes: the spring does not come out from the back — splitting the shell is the only way. A V3 gearbox with a quick-change spring guide is where swapping gets simple. If you are not comfortable opening a gearbox yourself, a tech shop will handle it.