Airsoft Spring M-Ratings Explained

Airsoft springs are rated with an "M" number, like M100 or M120, that roughly estimates the resulting muzzle velocity. An M120 spring, for example, typically produces somewhere around 400 FPS depending on the rest of your build. Always check your field's FPS limit before selecting a spring rating, since going over that limit gets your gun benched at chrono.

What do Airsoft Linear Springs Do?

A linear spring has evenly spaced coils along its entire length, delivering constant pressure through the compression stroke. This consistency comes at the cost of putting more overall stress on the gears and gearbox compared to a progressive design.

Airsoft Non-Linear (Progressive) Springs

A progressive spring has unevenly spaced coils that reduce compression resistance at the start of the stroke, easing the initial load on the gears and reducing wear and tear on the gearbox over time compared to a linear spring at the same overall power rating.

Replacing an Airsoft AEG Spring

Most AEG springs fit universally across standard gearboxes of the same version, though installing one still requires opening the gearbox unless you're running a quick-change spring system built specifically to avoid that step.

Airsoft Sniper and Spring Rifle Springs

Spring and sniper rifle platforms often use proprietary or rifle-specific spring dimensions rather than a universal fit. Match length and diameter to your specific model exactly, since a spring that's even slightly off spec for your platform can bind or fail to seat correctly.

Fine-Tuning FPS With Airsoft Spring Spacers and Clipping

Some players use spacers or carefully clip coils to fine-tune velocity up or down within a narrower range than swapping to a whole different M-rating would achieve, often to meet a specific field's FPS limit precisely rather than guessing at the nearest available spring rating.

What to Look for in an Airsoft Spring

A few details determine whether your spring choice delivers the power and durability you expect.

M-Rating vs. Your Field's FPS Limit

Confirm your target rating against your field's actual limit before ordering, factoring in your specific gun's other internals rather than assuming M-rating alone perfectly predicts FPS.

Linear vs. Progressive for Your Build

Progressive springs reduce gearbox stress over time. Linear springs offer more predictable, consistent pressure. Choose based on whether longevity or consistency matters more for your use case.

Platform-Specific Fit

For sniper and spring rifles specifically, match length and diameter exactly to your model rather than assuming a universal spring will seat correctly.

Airsoft Spring FAQ

What M-rating spring do I need for my field's FPS limit?

It depends on your gun's other internals as well as the spring itself, so treat the M-rating as an estimate and chrono your gun after installing to confirm actual FPS.

What's the difference between linear and progressive springs?

Linear springs apply constant, even pressure throughout the stroke. Progressive springs ease pressure at the start of the stroke, reducing gearbox wear over time at the same overall power rating.

Can I use any spring in any AEG gearbox?

Most AEG springs fit universally within the same gearbox version, but sniper and spring rifle platforms often need model-specific dimensions rather than a universal fit.

Do I need to open my gearbox to change the spring?

Yes, unless you're running a quick-change spring system built specifically to avoid a full gearbox disassembly.

Can I lower my FPS without buying a new spring?

Some players use spacers or carefully clip coils to fine-tune velocity within a narrower range, useful for hitting a specific field limit precisely rather than jumping to the next lower M-rating.