Spring Prometheus MS90 AEG

What distinguishes the Prometheus MS90 AEG spring is the non-linear setup that the manufacturer uses itself: a progressive spring. By that Prometheus means that the winding is not equally tight everywhere. In the places where the windings are close together, you feel less resistance than in the places where they are more widely distributed. For the teeth of the piston and gearbox, that works out favorably: they catch a much milder impact and are clearly less heavily stressed.

The progression starts gently. As the closely spaced windings reach each other, the stiffer, more widely distributed windings take over. In the final part of the compression, the pressure then increases anyway — comparable to how a linear spring would do that over its entire length.

That structure not only extends the service life of the internal parts of your airsoft replica. There is a second advantage to it: a strong motor gets the space to gather momentum before the heavy final compression, and that boosts your rate of fire. A logical upgrade for anyone who wants to spare the gearbox without sacrificing power.