HELP: FPS calculator - i need your input

so i’m adding a rudimentary muzzle velocity calculator to

what i need of the brains trust are some real life examples of your barrel ID, spring, gel weight and resultant FPS

unfortunately the airsoft calculation style isn’t a direct transfer

generally speaking i have gels weighing in @ 0.21g a piece

the goal with this calculator is to enable n00bs to select the most appropriate spring for the outcome they seek. its never going to be 1-2fps accurate so suck it up on that front :slight_smile: but if you know you need an M90 and not the M150 to achieve 280fps then…well…there’s that…

so…please send me:

bare minimum
barrel ID
gel weight
spring spec
fps achieved

of add directly to

the more detail i get the better i can make the calculation



Great idea @zeHamish. To double check though, I’m assuming you’re weighing the gel hydrated or is it you’re supposed to weigh it un-hydrated? Also will you need length of cylinder and barrel ‐ or is that already taken into account?

already working on in general - jelly to a tree and much approximation required…

but yes, gel weight MUST be hydrated

barrel ID = 7.0mm
gel weight = 0.22g [ausgel greens]
spring spec = M90 / 1.3mm
fps achieved = avg. 285

let me know if you need more info :smile:

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r u a legit m90 or a 1.3 with rough conversion to M90?

Now you got me questioning it haha. Had a 1.25 unequal and then upgraded to a legit m90 which under the verniers is a smidge over 1.3 wire diameter - also spring length was around the 170mm, though I can confirm once I pull it all apart again.

length is an important consideration…will need to look at how to factor that in.

what were you getting with the 1.25?

Closer to the 250 mark from memory, but had some different components which contributed to that limit. Different barrel id and length, ported cylinder.

I have lots of stats but I find the info so inconsistent with what hard ware upgrades I do.
I think unfortunately the variable x being the gel ball.
There is no way I’m going to sit their and grow gel balls on a flat bottom and and a dash of detergent or WD40.
It is a great idea I guess, the more on the field testing is also very useful.
Thats where I noticed today at a skirmish in the NQ bush where there was lots of wind my 330 fps which looked good in a chrono suffered severely with accuracy because a lot of the gel balls were not in tact.
This is where you need heavier gel balls and not the fabled milkies.

Indeed and I keep kit to run the heavies for windy wet days.

I’m hoping that with a decent data set I can get the fps approximation with 10fps of chrono accurate


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how long do you soke them for i thought ausgels wouldint fit a tight bore

a few things to look for when determining fps from a spring . what materiel is the spring made from . how long it is . how many coils it has. is it equal length . or unequal length

The look and material of a spring don’t seem to be as important as the performance. Take a look at Low Guidos videos on springs… he tests them by overall length, then he inserts a rod through a hole in his bench with a kilo of weight, Actually 2kg because I think he used a 2L milk bottle for the weight… so he puts the spring arond the rod poking up through the table, then puts a washer and a pin thru the rod… then measures how far down the weight pulls each spring and measures the compression length… here is that video (I think) :grin:

Just remember, Low Guido’s channel is the second best on the intertubes… even so, well worth a look like hail

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