Action Army Piano Wire AEG Spring

Main springs are consumables with opinions. The wire they are wound from decides how evenly they compress, how quickly they sag, and whether the rifle still chronos the same in March as it did in October. Action Army wind these from piano wire, which is the harder, more consistent end of the material scale.

Six ratings run through the range. The M95 is the gentlest, and Action Army put a one-joule figure against it; the M100 sits just above. Those two are the skirmish ratings that keep a rifle comfortably inside a UK site limit. From the M120 upward you are into tuning territory, and the M130, M140 and M150 only earn their keep on a build with the barrel, hop and ammunition to turn the extra energy into range rather than noise.

Changing a main spring is the first job anyone learns on a gearbox and the one most likely to be done badly. The spring itself is simple; closing the shell again without pinching a wire is the part that takes practice.

Specifications

Good to know before you buy

Chrono after every spring change, without exception. The same rating behaves differently depending on cylinder volume, air seal, barrel length and the weight of ammunition you feed it, so the number on the wire is a starting point rather than a result.

A heavier spring loads everything behind it. Piston, sector gear, bushings and motor all take more punishment, and the first part to complain is usually the one that was already tired. Worth looking over the rest of the gearbox while the shell is open.

The full ladder is here. All six Action Army ratings are listed, so you can step one rating at a time instead of jumping from an M100 to an M130 and hoping.

Spring and battery are one decision. A heavier spring pulled by an underpowered pack gives a slow, inconsistent first shot and a hot motor.

Frequently asked questions

Which rating keeps me inside a site limit?
Most UK skirmish limits sit around the M95 to M100 range on a standard setup, but that depends on your own gearbox, so chrono it rather than taking our word for it.

What is the one joule figure against the M95?
That is Action Army’s own designation for that spring. They publish no equivalent figure for the heavier ratings.

Why piano wire?
It is harder and more consistent than ordinary spring steel, which shows up as less sag over a season and a more repeatable chrono reading.

Do I need a new piston to go with it?
Not for the lighter ratings. Above an M100 it is worth checking the piston teeth and the first tooth in particular before you close the shell.

How long does a main spring last?
Until the chrono says otherwise. A spring that has sagged will read lower than it did when new, and that is the signal to change it.

Will this fit a version 2 and a version 3 gearbox?
Yes, it is a conventional main spring and not cut for one shell type.