Accuracy question from a first time Rolex owner (GMT II C brand new)

[MJK737]

I've noticed this also with my automatics with lower end movements. I'm pretty sure when your swinging your arms while running the balance wheel is not making a complete arc. The shorter arc of the balance wheel will speed up the watches amplitude thus making it run faster. After your run the balance wheel should swing normally thus settling down and becoming more accurate. Rolex uses shock protection and screws on the balance wheel to somewhat prevent this. Perhaps that is your issue? I run with my 16750 all the time and its pretty bang on. I did notice is sped up about 5 sec. once but that was a one time event. I use the USNO Master clock to check accuracy and I do so often. Bottom line is it's a mechanical watch and there's going to be some fluctuations.