Spring designation: interpretation.

[Gloutonguy]

Hi everyone I am relatively unexperienced with airsoft pieces and upgrades and I was wondering what does the number in the spring designation mean?

I often see things like M120 or M140, I guess it gives information about of the strength of the spring, but how can I have an idea of the fps a certain spring would give?

I searched and I did not find any thread concerning this, but I guess there might be one since it is a pretty important internal…

Thank you… and sorry for the question noobiness.

[Sha Do]

Obviously you did not search ...correctly. The M designation on a spring is simply the designation for meters per second. For example an M120 spring would net you around 120 meters per second.

Keep searching and you will find the spring charts for more information.

SHA DO

[Gloutonguy]

thanks

I just had no starting point for this search so I found all sort of info about test but they never said anything about the meaning of the designation. That's a bit what meant by "I did not find anything"

Anyway thanks again. I'll rexsume my searches.

[CDN_Stalker]

Don't need an M in the type at all, many springs don't yet have a meters per second rating. Literally, any spring between 90 and 190 will be m/s rating, so take the number and multiply by 3.3 and you'll get a rough idea.

Also, there are springs that have a % rating, first of all they are largely flaky (made by PDI), same rating in the past has been different lengths and strengths, I've had PDI 150% springs that ranged from 6 3/8" to 7" long, made of different thicknesses of wire, and put out anywhere between 350fps and 425fps.

Add in, different manufacturers will have springs of the same ratings, but different outputs for some reason (likely test rig differences). I used to have a Prometheus 110 spring that had a constant output of 360fps in my MP5, yet a Madbull 110 would net me 415fps.

[m102404]

I had the same question when I started. Here's a short note about it...lots of other stuff written and stickied throughout the site.

Different manufacturers note their springs differently.

Some springs are noted in Meters Per Second (M/s)...typically with a "M" in front of a number. I.e. M90/M100/M120

Some springs are noted in Percentage %....i.e. 100%, 150%, 200%

Some springs are noted otherwise...i.e. Modify notes their springs with "S", S90+, S100+....and in Modify's case it's the same as M/s

The baseline of spring power is Tokyo Marui's stock power level which was approx 290fps (feet per second measured with 0.20g BBs). That is approximately a M90 spring.

Approx 1M/s = 3.3fps...so M90= 90M/s = 90 * 3.3 = 297fps
M100 =~ 330fps, etc....

TM's stock M90 spring is considered 100%...so a 150% spring is 90M/s * 150% = 135M/s = 135 * 3.3 = 445.5fps. (give or take 10fps)

The fuzzy part about it all...is that those numbers are HUGELY impacted by other parts that you may have in your mechbox/rifle...and the condition/fit of those parts. A bearing spring guide might add 5fps...might add 10fps with a different spring. A tightbore might add 5fps in one barrel length and add 10fps in a different tightbore barrel length. If you piston head seals badly or your nozzle leaks you might not get the full potential out of a given power spring to begin with...etc.etc.etc. Welcome to fiddling with AEGs.

Compounding all that...the way/consistency some manufacturers do their springs may mean that while they label one spring M100 and another M120....their M100 might not be the same as another manufacturers M100....and their M120 might not be "20M/s faster" than their own M100! Stick to trusted brands of springs to minimize those headaches.

A great read is Skruface's What to upgrade or not (stickied)...Greylock's stickied thread as well. Illusion's spring chart has been stickied here and there all over the Internet.

A general rule of thumb with a decently working rifle is...stick to a M90/M100 if you want to stay under indoor limits. A M110/M120 will put you very close and maybe over outdoor limits.

*edit* or what Stalker said (but look at the top of the Upgrades section for Skruface/Greylock/Illusion's stickied threads)

[Gloutonguy]

Well, thanks everyone for such a complete answer !