Im tryng to recalibrate my esteps now that im using 2.85mm filament instead of 3mm
recommended esteps for my Bondtech v2 extruder is 510

Using a Caliper i mark out 150mm of filament. I then extrude 100mm so I should have 50mm left if all goes well.
I then use this calculation to determine my new estep value
(old estep value * 100) / (150mm - amount remaining)

I have tried it several times and each time im getting a different result. that can vary 30-40 esteps.
I thought that perhaps my extruder was slipping because im using a thinner filament but that isnt it.. its been tightened and its grip is strong.. its not grinding.. no residue on the hobbed gears. its not skipping steps. and it has ample amps allocated.

Not sure whats going on.