I do however think that it is VERY gun depedent.
For example my phantom is +-3 on c02 on a bad day... I have gotten +-1 at times. (I chrono and 3 shots read the exact same fps). On hpa I get +-10 on bad days. I will do a test replicating yours with my phantom tomorrow to see if this is true... but experience tells me it is.
And I am moving this OUT of the experiment vault... doesn't belong here yet. Bryce or CockerPunk, lemme know if I am wrong to move this.
I would love to see you prove that you get (+/-) 1 fps. In fact, head over to the Paintball ASTM thread and download the Kuhnley-Gansner Standard Consistency Test (KGSCT) and do the testing. I think you will find that your marker will have a hard time beating (+/-) 4 fps tops.
Here is the BETA (KGSCT):
I am not lying when I say I have walked up to the chrono, taken 3 consecutive shots and not had the chrono readout change. Then someone else uses it (I thought it was broken honestly) and it varied every shot for them. Then I used it and it was dead on for another shot, then it varied 1 fps, then it went back to the original number. I kid you not... I really wish I had video proof of it. It was my second time ever using a phantom... I was pretty shocked. I have however seen it before maybe once a month or so, +-1 isn't TO hard.
That 289-291 fps.