Nerf Spring Ratings Explained: What Do 1.4, 1.6 and kg Tell You?
Buy a spring by its exact blaster fitment and full specification, then use the label to distinguish options within that supported range. A bare “1.4”, “1.6” or “10 kg” does not identify a universal Nerf spring. It cannot establish which receiver it fits, how much force you will feel at the grip, or what FPS your darts will produce.
The most useful habit is keeping three questions separate: what the part is, whether it fits, and what the completed blaster does with it. Confusing those questions is how a plausible-looking spring ends up being the wrong purchase.
Read the unit as well as the number
| Label or measurement | What it can tell you | What it cannot establish alone |
|---|---|---|
| Decimal such as 1.4 or 1.6 | A maker's option label; when explicitly specified in mm, it may identify wire thickness | Universal spring rate, fit or FPS |
| Free length in mm | Uncompressed spring length | Available travel inside the assembled blaster |
| Outside / inside diameter | Clearance around a guide or inside a housing | Compatibility with catch and full compression |
| Rate in N/mm | Force change per unit compression | Complete blaster performance |
| Load label in kg | A seller's load designation requiring its test condition | A directly comparable rate without deflection information |
Decimal labels need a definition
When a seller explicitly states that a decimal is wire diameter, read it as a dimension, not a kilogram rating. When the listing simply says “1.6 spring”, retain that product label and ask for the missing definition rather than silently supplying one. The same number on two platforms is insufficient evidence that the parts are identical.
Spring manufacturer Lee Spring treats wire diameter, coil diameter, free length and coil count as distinct design variables. Changing one can affect more than one behaviour. Therefore, even confirmed equal wire thickness does not make two springs equal in rate or compressed dimensions. The practical consequence is simple: matching the visible number is not a substitute for a supported part listing.
A kilogram label needs a compression condition
Force at a particular compression and spring rate are different specifications. A load label only becomes meaningfully comparable when the supplier explains the installed or test length associated with it. Ask what the rating means for that product rather than treating two sellers' kilogram labels as a standardised laboratory result.
Likewise, a main spring's load is not automatically the force measured at your priming grip. The blaster mechanism, friction and the point in the stroke affect the operation you feel. Choose a supported spring you can cycle comfortably, and avoid converting between a decimal option name and kilograms with an internet rule of thumb.
The Harrier provides a concrete example
The Worker Harrier 1.6 listing offers 250 mm and 300 mm spring lengths under the same decimal label. Its published results vary with spring length, barrel and dart type. That directly demonstrates why “my Harrier has a 1.6” is an incomplete description.
A useful build record includes the exact product, selected length, installed barrel, dart model and muzzle attachment. Record measured output separately. If you ask for help later, that information gives the shop something actionable; a spring number followed by a single best FPS reading does not.
Check fit before chasing output
Confirm the exact platform and variant named on the part listing. Ask whether other components are required and follow the maker's installation procedure. If the action cannot complete its intended movement or engage correctly, stop and identify the mismatch. Do not trim a spring or force the mechanism solely because the catalogue number looks close.
After a supported installation, chronograph a repeatable shot string with the darts used at your venue. Compare the full result with the event requirement, then record the configuration. The S400 1.5 spring, for example, is a platform-specific lower-output option; its listing estimate is not a guarantee for every modified S400.
Frequently asked questions
Is a 1.6 spring always stronger than a 1.4?
Only compare within a maker's defined, compatible range. The labels alone do not rank unrelated springs.
Can I convert 1.6 into kilograms?
Not from that number alone. You need the defined specification and compression condition.
Will the advertised FPS be my result?
It is a reference for the described setup. Measure your own spring, barrel and dart combination.
Products mentioned
Related reading
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Specifications checked 19 October 2026. Manufacturer and product-listing claims are distinguished from editorial buying advice; no new hands-on measurements are claimed here.